6.1 Genetics and Evolution Flashcards

Question

RNA processing - Post-transcription/Pre-translational control

Answer 1

Pre-mRNA is transformed into mature mRNA. A cap is added to the 5' end and a tail is added to the 3' end. This stabilises the mRNA and delays degradation aswell as assisting with binding to ribosomes. Splicing also occurs where the RNA is cut at specific points - introns(non-coding) are removed and the exons(coding) are joined together. All inside the nucleus

Answer 2

the nucleotide sequence of some mRNA molecules can also be changed through base addition, deletion, or substitution. This has the same effect as point mutations and results in the synthesis of different proteins which may have different function. This increases the range of proteins that can be produced from a single mRNA molecule or gene.

Answer 3

degradation of mRNA - the more resistant the molecule the longer it will last in the cytoplasm, the greater quality of protein synthesised. binding of inhibitory proteins to mRNA prevents it binding to ribosomes and the synthesis of proteins. activation if initiation factors which aid the binding of mRNA to ribosomes (the eggs of many organisms produce large quantities of mRNA which is not required until after fertilsation, at which point intiation factors are activated.

Answer 4

They are enzymes that catalyse the addition of phosphate groups to proteins. The addition of a phosphate group changes the tertiary strcutre and so the function of the protein. Many enzymes are activated by phosphorylation. Protein kinases are therefore important regulators of cell activity. Protein kinases are themselves often activated by the secondary messenger cAMP.

Answer 5

It involves modifcation to the proteins that have been synthesised. - addition of non-protein groups such as carbohydrates chains, lipids or phosphates. - modifying amino acids and the formation of bonds such as disulfide bridges. - folding or shortening of proteins - modification by cAMP - e.g. the lac operon, cAMP binds to the cAMP receptor protein increasing the rate of transcription of structural genes.

Answer 6

The regulation of the pattern of anatomical development

Answer 7

They are small, easy to keep, and have a short life cycle so have always been a popular choice for genetic studies.

Answer 8

a group of genes which contain homeobox. Homeobox is a section of DNA 180 base pairs long, 60 amino acids that is conserved in animals, plants and fungi. The homeodomain part of the protein binds to DNA and swtiches other genes on or off. It is a regulatory gene. Many homeobox genes still present in the mouse and human, still have identical nucleotide sequences

Answer 9

It is one of the homeobox genes. When mutated it causes a form of blindness in humans. Mice and fruit flies have this gene and disruption of the gene causes blindness in these organisms aswell.

Answer 10

They are a group of homoebox genes only present in animals. They are responsible for the correct positioning of body parts. In animals the hox genes are found in gene clusters - mammals have 4 clusters. The order of which the genes appear along the chromosomes is the order in which their effects are expressed in the organism. Humans have 39 hox genes which have arrise from mutations.

Answer 11

Body plans are presented as cross sections showing the tissue layers arrangement. Diploblastic animals = 2 primary layers Tripoblastic animals = 3 primary layers Animals are segmented. These segments have multiplied over time and they are specialised to form a function. Hox genes in the head control the development of mouthparts and hox genes in the thorax control the development of wings, limbs or ribs. Somites are are directed by hox genes to develop in a particular way depending on their position in sequence

Answer 12

The body shape of most animals shows symmetry - Radial symmetry is seen in diploblastic animals like jellyfish. They have no left or right sides, only a top and bottom - Bilateral symmetry - have a left and right side and a head and tail - Asymmetry is seen in sponges which have no lines of symmetry

Answer 13

Mitosis is cell division whilst apoptosis is cell death. The role of mitosis is to increase the number of cells leading to growth. The role of apoptosis is to remove unwanted cells and tissue to shape the body parts. Cells undergoing apoptosis can also release chemicals signals which can stimulate mitosis and cell proliferation leading to remodelling of tissues.

Answer 14

It was a drug taken for morning sickness during pregnancy in the 1950s and 60s. It was discovered that it prevented the normal expression of a particular hox gene. This resulted in babies born with shortened limbs. It has been exploited to be used to treat some types of cancer and stop the development of some cancers. It is believe that thalidomide prevents the formation of netwroks of capillaries which are necessary for some tumours to grow and develop.

Answer 15

Programmed cell death

Answer 16

Apoptosis is controlled meaning it occurs due to cell signalling wheras necrosis is uncontrolled cell death which means it is not programmed. Necrosis occurs through trauma

Answer 17

Enzymes breakdown the cells cytoskeleton They cytoplasm becomes dense with densely packed organelles. The cell surface membrane changes and blebs form. Chromatin condenses, the nuclear envelope breaks and DNA breaks into fragements. These are all packed into vesicles Phagocyte cells ingest the vesicle so the debris doesn't damage other cells

Answer 18

Apoptosis is used to remved webbing between the limb digits. e.g. At week 6 the webbing is present but at week 20 apoptosis has removed the webbing and each digit is formed

Answer 19

as a tadpole grows into a frog, apoptosis is used to destroy the tadpoles tail whilst cell differentiation and growth grow its other limbs

Answer 20

normal body cells divide 40-60 times before they start to undergo apoptosis

Answer 21

adult - 50-70 million/day child - 20-30 billion/day

Answer 22

children are developing so the removal of unwanted cells is required. Adults are alwyas removing damaged cells, aswell as removing viral cells or DNA damaged cells.

Answer 23

If apoptosis is high cell loss and degeneration of tissues can occur could cause autoimmune disease e.g. arthritis, lupus If there is low levels of apoptosis = could form tumours

Answer 24

Cell signalling involing receptor ont eh cell surface membrane Positive signalling - prevents apoptosis apoptosis inhibitor proteins found in cytoplasm Negative signalling - triggers apoptosis inducer signals produced in damaged cells signals identify cell as damaged and trigger apoptosis cytokines - trigger phagocytes

Answer 25

A condition where some plants appear yellow or pale because the cells in the plant aren't producing the normal amount of chlorophyll.

Answer 26

Lack of light - plants will turn off their chlorophyll production to conserve resources. Mineral deficiencies - e.g. a lack of iron or magnesium. Iron is needed by some cofactors for enzymes that produce chlorophyll. magnesium is found at the heart of the chlorophyll molecule. Virus infections - viruses interfere with the metabolism of cells.

Answer 27

A mutation on chromosome 7 can lead to alternative fat deposits in the body. As a result the body will become obese alongside other factors

Answer 28

Genotype - The genetic make up of an organism Phenotype - The observable charecteristics

Answer 29

Dominant - a version of the gene that will always be expressed Recessive - will only be expressed if there are two copies of it

Answer 30

Homozygous - has two identical alleles for a charecteristic. Could be dominant or recessive Heterozygous - they have two different alleles for a charecteristic. In this case the allele for the dominant phenotype will be expressed.

Answer 31

DIscontinuous variation will have distinct groups controlled by one gene most of the time whilst continuous variation will have many genes controlling it as well as the environment which results in a continuous variation.

Answer 32

Shows how genes are passed on from parents to their offspring.

Answer 33

The inheritance of a single gene.

Answer 34

1. State the phenotypes of the parents 2. State the genotypes of both parents stating in terms of dominant and recessive alleles 3. State the gametes of each parent 3. Use a punnet square to show the results of the random fusion of gametes during fertilisation. Labelling the gametes on the edges of the square 5. State the proportion of each genotype which are produced. Ratio or proportions 6.State the corresponding phenotype

Answer 35

Two individuals who are pure breeding were crossed producing heterozygous offspring as the F1 generation. Then the F1 generation was crossed and produces a ratio of 3:1 by phenotype. This is the F2 generation.

Answer 36

Codominance occurs when 2 different alleles occur for a gene both of which are equally dominant. So both alleles are expressed. Example: Snapdragon flowers. White and Red are both codominant. The alleles code for enzymes which produce the specific pigments. When both are present it produces Pink flowers The letters for codominance are written as a capital and then a small letter for the specific allele to show that they aren't dominant.

Answer 37

This is where there are more than two alleles for a gene, however, only 2 can be displayed. They will be dominant and recessive to each other. Example: Blood groups Ia, Ib, Io. Ia, Ib are both codominant over Io. If both codominant are present then they produce a AB blood group. Blood group O is only when both are O.

Answer 38

Women - XX Men - XY The 22 chromosomes are all the same in humans. The 23rd chromosome is the sex chromosome. The X chromosome is common and larger. The second could be X or Y. Y is much smaller and contains nearly no genetic information beside deciding the embryo will develop as a male.

Answer 39

Some genes are only carried on the X chromosome of the 23rd chromosome since the Y chromosome is much smaller. There are a number of genes that males will only have one copy of. This means if a recessive allele is present on the X chromosome then they will have the condition. example: Red-green colour blindness is more common in males, because they have only one copy of the gene on the X chromosome.

Answer 40

Patients with haemophilia have blood which clots extremely slowly due to the absense of a protein blood-clotting factor. As a result injury can result in prolonged bleeding which is potentially fatal. A male may inherit a recessive allele on their X however they cant have a allele on their Y to cover this. Females who are heterozygous are carriers and may pass it onto their children.

Answer 41

The dominant sex linked allele should be written as X^capital letter. Recessive as X^lowercase and Y as Y.

Answer 42

The inheritance of 2 genes. Shown by dihybrid crosses.

Answer 43

Used to show the inheritance of two different charecteristics, caused by 2 genes, which may be located on different pairs of homologous chromosomes. A dihybrid cross shows four alleles at each stage instead of 2.

Answer 44

Pea plants. Seeds can be 2 colours - Yellow or green, and 2 shapes - round or wrinkeled. Y - Yellow y - Green R - round r -wrinkled

Answer 45

chromosome that is not a sex chromosome Genes on the same chromsome are linked.

Answer 46

Crossing over during meiosis (prophase 1) Independent assortment during meiosis 1

Answer 47

If two genes are autosomally linked, you won’t get the phenotypic ratio you expect. For dihybrid you would usually expect (9:3:3:1) If two genes are inherited together it is more like a monohybrid cross (3:1)

Answer 48

they are inherited as one unit because they are so close to each other on the chromosome and aren't separated by independent assortment or crossing over.

Answer 49

It is a measure of the amount of crossing over that has happened in meiosis. Recominant frequency = number of recombinant offspring/ total number of offspring. 50% means there is no linkage and the genes are on separate chromosomes. Less than this means there is gene linkage and the random process of independent assortment has been hindered.

Answer 50

It is a statistical test used to measured the size of the difference between the results you observe compared to the expected results and can be used to determine if the results are significant.

Answer 51

Hypostatic - masked by another gene Epistatic - affects the expression of another gene.

Answer 52

If a phenotype to be expressed requires a process of 4 genes where they are passed from one gene onto the next. If one of the earlier genes fails to work then the rest of the gene will not be displayed, which means the final genes are masked by the other genes, which are the epistatic genes.

Answer 53

Recessive epistasis - if the presence of 2 recessive alleles at a gene locus led to the lack of an enzyme then it will called recessive epistasis. Dominant epistasis - When a dominant allele masks another gene. Only 1 is required to do this.

Answer 54

Labrador colours One gene codes for the production of pigments and has the alleles B(dominant, black pigment) and b(recessive, brown pigment) A second gene codes for where the pigment is deposited and again has 2 alleles: E(dominant, pigment deposited in skin and fur), e(recessive, pigment deposited on skin only)

Answer 55

1. 95 degrees - hydrogen bonds break 2. 50-65 degrees - primers can anneal 3. 72 degrees - Taq DNA polymerase binds new nucleotides to the template strand Produces 2 copies

Answer 56

To multiply the genetic material available

Answer 57

Add an agarose gell to a gel tray ad solidify, with rows of wells . Add buffer solution at the sides of the gel box so surface is covered. Load DNA samples in the well Put the lid on the box and and an electrical current is applied. DNA fragments move from negative to positive . Small DNAs travel faster. Let it run till the end of the tray and then turn off power. Remove the gel tray from the gel box and tip off any excess buffer solution. Stain the DNA fragments by covering the surface with stain.

Answer 58

RNA - same method Proteins - they need to be denatured since they can have both charges, so they have the same charge.

Answer 59

Use restiction enzyme Restriction enzymes can recognise specific sequences such as minisatelites and microsatelites and palindromic sequences. The digest the DNA at these place. The enzyme is complementary to specific sequence. THe sample and enzyme are incubated to cut the sample. They may lave sticy ends which are small tails with unpaired bases.

Answer 60

First PCR is used to multiply the DNA sample that is present THen electrophoresis is used to produce the DNA profile

Answer 61

An organisms genome contains repetitive non coding base sequences - that dont code for proteins and repeat. the number of repeats and length differs between people the number of times it is repeated in the same loci can be analysed through electrophoresis creating a DNA profile. The chance of 2 people having the same DNA profile is very low because the chance of 2 people have the same number of repeats at each locus in DNA is very low.

Answer 62

the DNA sample collected is compared to possible suspects, to link them to crime scenes. THe PCR products are run on and electrophoresis gel and compared to see if their are any matches. And this lets you link people to the crime scene.

Answer 63

a DNA profile can refer to a unique pattern of several allels. It can be used to analyse the risk of genetic disorders. It's useful when the specific mutations isnt know or where several mutations could have cause teh disorder.

Answer 64

It is the manipulation of an organisms DNA. Organisms have their DNA altered by genetic engineering and they are called transformed organisms These organisms have recombinant DNA - DNA formed by joining together DNA from different sources. A gene is extracted and inserted into another organism

Answer 65

Producing DNA fragments using reverse transcriptase 1. mRNA is extracted from cells 2. mRNA is reverse transcribed using the reverse transcriptase enzyme 3. This makes a cDNA strand identical to the original DNA and the cDNA is isolated from the mRNA strand 4. cDNA, free nucleotides are the DNA polymerase can then orm the otehr strand of DNA, reforming the desired gene.

Answer 66

1. Desired gene is obtained using restriction enzyme or reverse transcriptase of mRNA 2. The DNA fragment is inserted inot a vector using DNA ligase. The vector is cut open using the same restriction enzyme. 3. THe vector transfers the gene into the bacteria This is through electroporation. . A machine produces an electrical field and it will increase the permeability of the bacterial cell membranes and allows them to take it in.

Answer 67

A plant crop can be genetically modified by having a gene inserted which makes them resistant to insect pests.

Answer 68

Many pharmaceuticals are produced using GM organisms. This is a process called pharming

Answer 69

Soybeans have a gene from Bt Bacteria which codes for a toxic protein to some insects. The toxic gene is isolated using restriction enzymes and inserted into a plasmid. The soybeans are deliberately infected with the plasmid.

Answer 70

For treatment of Hereditary antithrombin deficiency: People with this cant produce blood clots efficiently DNA fragments that code for the production of antithrombin are extracted from mammary glands and injected into goat embryo. The embryo is implanted into a femal goat. When the offspring is produced it is tested to see if it produces the antithrombin protein. Selective breeding is used to produce a herd of goats that produce antithrombin in their milk. The protein is extracted from the milk and used to produce a drug that can be given to people with the disorder.

Answer 71

Scientists carry out research into GE pathogens in order to find treatments for disease. e.g. 1. Scientists found that some tumour cells have receptors for poliovirus - so poliovirus will attack them 2. Scientist can use to kill cancer cells by GE the poliovirus genes

Answer 72

People worry that scientists doing the research could become infected with the live pathogen and potentially cause a mass outbreak of disease The GM veersion of pathogen could revert bck to its orignal form and cause an outbreak of disease In the wrong hands, it can create dangerous pathogens used in biowarfare.

Answer 73

The original scientist will get a patent for their work so they can control who uses it and for how long. This is good because it increase competition for scientists to be the first to come up with the idea However farmers in poorer countries may not be able to afford the patented good. This is unfair on poor farmers.

Answer 74

Gene therapy involves altering alleles inside cells to cure genetic disorders Process depends on whether it is caused by dominant allele or recessive allele: - 2 recessive alleles: you can add a working dominant allele to make up for them - 1 dominant allele you can silence the dominant allel by sticking a bit of DNA in the middle of the allele so it doesn't work anymore To get the new allele inside the cell you insert it using vectors such as altered viruses, plasmids, or liposomes

Answer 75

Somatic therapy - Altering allels in body cells which are affected by the disorder. E.g. cystic fibrosis. Offspring can still inherit the disease Germ line therapy - involves altering the allels in the sex cell. This means every cell of any offspring will be affected by the gene therapy and wont inherit the disease. ILLEGAL

Answer 76

Prolong lives of people better quality of life Allows people to conceive a baby without the risk of passing on disease (GL therapy) Decrease the number of sufferers

Answer 77

Could be used for other treatments such as cosmetic effects of ageing Potential to more harm than good Expensive May be short live (somatic) Patients may have to undergo multiple treatments body could identify vectors as foreing bodies and start an immune response An allele could be inserted into the wrong place overexpressed alleles

Answer 78

Mixture of A ssDNA template, DNA primer, DNA polymerase, Free nucleotides, Free fluorescently labelled nucleotides, 1. The sample undergoes PCR so there are many strands of DNA however they will all be terminated at different points depending on where the modified nucleotide was added. 2. DNA samples are separted by electrophoresis and visualised under UV light. 3. The complementary base sequnce can be read from the gel. The smallest nuccleotide is at the bottom of the gel. Each band represents on more base added. So by reading from the bottom you build up the gene sequence.

Answer 79

A genome is cut into smaller fragments using restriction enzymes The fragments are inserted into Bacterial artificial chromosomes (BACs) - man made plasmids The BACs are then inserted into bacteria - each bacterium contains a BAC with a different DNA fragment. The bacteria divides creating colonies of clones. DNA is extracted from colonies. It is the cut up producing overlapping pieces of DNA. Sanger sequenced and the pieces are put back in order to give the full sequence from the BAC DNA sequences are put back in order

Answer 80

Hundreds of sequences can run in parallel. It is automated and faster - contains all the modified nucleotides - each with a fluorescent label and the machine reads the sequence for you. Pyrosequencing doesn't use electrophoresis - next gen sequencing - can sequence millions of DNA molecules at the same time - much faster than sanger sequencing.

Answer 81

By sequencing a gene, the sequence of amino acids that the gene codes for can be predicted and so the primary structure of the polypeptide can be predicted. This has allowed biological molecule to be produced from scratch - synthetic biology

Answer 82

Computational biology - using computers to study biology e.g. create computer simulations and mathematical models Bioinformatics - developing and using computer software that can analyse and store biological data.

Answer 83

An organics phenotype can be predicted by sequencing its genotype e.g. Marfan syndrome is a genetic disorder caused by a mutation of the FBN1 gene. This mutation on the gene affects what symptoms a person with Marfan syndrome will have. This allows scientists to develop genotype - phenotype correlations.

Answer 84

The study of health and disease within a population considers the distribution of disease, its causes and its effects. Some gene mutations have been linked to a greate risk of disease. Computerised comparisons between the genome of people that have a disease and those that don't can be used to detect particular mutations

Answer 85

Closely related species share more DNA. Whole genome can be sequence and analysed to see how much they relate.

6.1 Genetics and Evolution Flashcards

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