Unit 4 Flashcards

Question

How does the process of random fertilisation alter variations in the genotype of offspring

Answer 1

Random Fertilisation * Genetic variation is also introduced by random fertilisation of the gametes produced by meiosis. * Any of the genetically unique sperm generated by a male may fertilise the genetically unique egg produced by a female.

Answer 2

the molecular unit of hereditary information

Answer 3

all the genetic material in the chromosomes of an organism including its genes and dna sequences

Answer 4

* EXONS * The part of the gene that codes for a protein

Answer 5

Regions of DNA that do not encode protein sequences Noncoding Sequences include: * A variety of regulatory control elements maintain transcription of nearby genes (e.g. promoters) * Instructions to make certain types of functional RNA (tRNA, rRNA etc.) * Centromeres * Telomeres (caps on the end of DNA that prolong the chromosome’s life) * Introns (noncoding parts of genes that are transcribed into mRNA, but then removed by RNA splicing before transcription).

Answer 6

The genetic code is a triplet code. * Three nucleotide bases code for one amino acid. * The code in non-overlapping, as each base is part of one codon. * It is also degenerate, where different codons code for the same amino acid.

Answer 7

>Transcription is the mechanism by which the base sequence of a gene on a DNA strand is converted into the complementary base sequence of mRNA. STEPS 1. RNA polymerase links to DNA at the beginning of the sequence to be transcribed. - Only one of the DNA strands is used as a template. 2. As RNA polymerase moves along the strand, it picks up appropriate free RNA nucleotides from to nucleoplasm. - It joins guanine to cytosine and uracil to adenine. - This happens until it reaches a terminator sequence is reached. 3. The pre-mRNA detaches from the template strand. - It is thus a copy of the base sequence on the coding strand of the length of DNA. - The two DNA strands join by complementary base pairing, and it winds back into a double helix. Splicing in Transcription * The pre-mRNA must be modified before it leaves the nucleus. Chemicals are added to ensure stability and introns are removed by splicing. * Exons are spliced together differently, producing different final polypeptides. * After splicing, the mature mRNA leaves the nucleus and goes to ribosomes located in the cytoplasm.

Answer 8

>Translation by ribosomes allows assembly of amino acids into polypeptides according to the original DNA code. STEPS 1. mRNA attaches to a ribosome. 2. tRNA has an anticodon on one end and an amino acid bonded to the other, which it carries to the ribosome. 3. The tRNA anticodon binds itself to the first coon on mRNA due to complementary base pairing. 4. Another tRNA molecule binds to the second codon of the mRNA. 5. The Amino Acids join by a peptide bond and the tRNA molecules detach themselves. 6. This is repeated leading to the formation of a polypeptide chain (continues until a stop codon reached).

Answer 9

The purpose of gene expression is the synthesis a functional gene product (protein or functional RNA) * That the process can be regulated and is used by known life. * These products are mainly proteins, but in non-protein coding genes such s tRNA genes, the product would be functional RNA.

Answer 10

1. Point Mutations - Usually take place during replication. - Occur when a single nucleotide base is changes in a sequence of DNA or RNA - Includes non-synonymous substitution mutations. - Top image

Answer 11

- Usually take place during DNA Replication - Caused by insertion or deletions of several nucleotides in a DNA sequence that is not divisible by three. - Due to the triplet nature of gene expression by codon, the insertion or deletion can change the reading frame. - This results in a completely different translation from the original. - Bottom image

Answer 12

Nondisjunction: results in daughter cells with abnormal chromosome numbers (known as aneuploidy)

Answer 13

Occur in somatic cells and are not passed onto offspring.

Answer 14

Occur in cells that give rise to gamete and are often passed onto offspring

Answer 15

The location of a Gene on a chromosomes

Answer 16

Chromosome pairs, one from each parent, that are similar in length, gene position and centromere location. Diploid cells contain these (2n)

Answer 17

a version of a same gene, they specify different versions of the same trait and are found in same

Answer 18

Observable characteristics of an organism.

Answer 19

Alleles present within cells of an individual, for a particular trait or characteristic

Answer 20

Characteristic in which the allele responsible is expressed in the phenotype, even those with heterozygous genotypes.

Answer 21

Characteristic in which the allele responsible is only expressed in the phenotype if there is no dominant allele present.

Answer 22

Where both alleles in a pair are identical (homozygous recessive (aa) or homozygous dominant (AA))

Answer 23

When the alleles in a pair are different (Aa or Rr)

Answer 24

Any chromosome that is not a sex chromosome

Answer 25

Used to consider the inheritance of one characteristic and consider complete dominance. * most traits follow the dominant/recessive pattern of inheritance, whereby one allele is expressed over the other. * The dominant allele will mask the recessive allele when in a heterozygous state. * Homozygous dominant and heterozygous forms will be phenotypically indistinguishable as they both present the dominant phenotype completely (hence why it is complete dominance) * Punnet squares as is the image to the right are used These monohybrid crosses follow two of Mendel’s Laws 1) The Law of Segregation - An organism has two alleles but can only pass on one. - The two alleles for a trait separate during gamete formation. 2) The Law of Dominance - One trait may be masked by another trait, as some alleles are dominant, and others are recessive.

Answer 26

Sometimes, different characteristics are inherited at the same time such as: * Height and eye colour. * Freckles and dimples * Hair colour and tounge rolling. Dihybrid crosses are those where we consider the inheritance of two characteristics at the same time. This overs Mendel’s Third Law Mendel’s Third Law: The Law of Independent Assortment. * Factors or a trait separate independently of one another during gamete formation. * Genes found on separate chromosomes are inherited independently of each other.

Answer 27

When two true-breeding parent cross to produce and intermediate offspring (a combination of both phenotypes). Heterozygous however both alleles are equally expressed. In the snap dragon, a cross between homozygous white flowered plant (C^w C^W) and a homozygous, red-flowered plant (C^R C^R) will produce offspring with pink flowered (C^R C^W)

Answer 28

Codominance occurs when pairs of alleles are both equally expressed in the phenotype of a heterozygous individual. Heterozygous therefore will have an altered phenotype as the alleles are having a joint effect. When representing alleles, the convention is the use subscripts for the different codominant alleles. * Recessive is still in lover case. * An example can be seen on the right.

Answer 29

Codominance in Blood Groups (shown a lot in past EAs) * Human red blood cells can be categorised into different blood groups based on the structure of a surface glycoprotein (ANTIGEN) * ABO blood groups are controlled by a single gene on the surface of red blood cells. * The A and B alleles are codominant. * The O alleles are recessive and does not modify the basic antigenic structure. * When representing blood groups, the letter I is used to represent different antigenic forms (isoagglutinogen) * A allele = IA * B allele = IB * O allele = i (recessive).

Answer 30

SEX LINKED INHERITANCE Sex linkage is the phenotypic expression of an allele that is related to the chromosomal sex of an individual. Since there are far more genes on the X chromosome than the Y, there are far more X linked traits than Y linked traits. Males are more subject to sex linked disease as they have heterogenous sex chromosomes (XY) whilst female have homogenous (XX). * It is harder to have a disease on both X chromosomes than just one. * If a female has the disease on only one X chromosomes, there a carrier but usually asymptomatic. * Males, however, are almost always phenotypically symptomatic to X-linked disease.

Answer 31

Polygenetic inheritance is used for complex traits such as hair colour or skin colour. * When a characteristic is controlled by two or more genes. * For eye colour, the actual number of genes involved may be between 6 and 16. * For skin colour and hair colour it is a similar amount.

Answer 32

STEP 1: Isolation * a restriction enzyme recognised a target sequence and cuts DNA into two pieces at or near that site (recognition site). * Most restriction enzymes produce cut ends with short, single-stranded overhands called sticky ends. * If two molecules have matching overhangs, they can base-pair and stick together. * Some however, produce bunt ends. STEP 2: Prepare the Plasmid * Use the same restriction enzyme from step one to make a single cut of plasmid. * This is going to be the plasmid vector that is inserted back into a bacterium. STEP 3: Glue in the DNA * DNA ligase acts as glue and seals gaps in the DNA backbone. * Therefore, when it is used in recombinant DNA, it will link the plasmid and the DNA fragment to make a recombinant plasmid containing the gene. * DNA ligase links the phosphate group o one DNA strand to the hydroxyl group of the other DNA strand to form a singular phosphate backbone/combined piece of DNA. STEP 4: Bacterial Transformation * Plasmids can be introduced into bacteria in a process called transformation. * Pre-prepared bacterial cells are given heat shock to encourage them to take up foreign DNA. * Plasmids normally also contain and antibiotic-resistance gene, so this is an easy way to see which bacteria took it up. * You can grow the bacteria on agar plates that have been applied with an antibiotic. - If they survive it has succeeded.

Answer 33

MAPPING GENOMES DNA sequencing is the process of determining the nucleic acid sequence in DNA. Applications of DNA sequencing include mapping genomes. They allow us to compare the DNA of closely related species in order to establish and analyse their genetic differences, a field known as comparative genomics.

Answer 34

PURPOSE OF PCR * Enables us to extract a tiny quantity of DNA from a single hair or drop of blood and increase the amount of it millions of times so that it can be analysed. * Can also be done to determine if a bacterial or viral infection is present. * Makes it possible to mass produce DNA even from fossil remains.

Answer 35

Gel Electrophoresis is a form of DNA profiling that determines an individual’s DNA characteristics. * Help identify unique genetic information and forensics. * Helps separate DNA into fragments based on size. * DNA molecules are negatively charged, so if u apply an electrical current to a medium they’re present in, they will move toward the positive electrode.

Answer 36

Change in the genetic composition of a population during successive generations which may result in the development of a new species.

Answer 37

Small-scale variation of alleles frequencies within a species or population, in which the descendant is of the same taxonomic group as the ancestor.

Answer 38

The variation of allele frequencies at or above the level of species over geological time, resulting in the divergence of taxonomic groups, in which the descendant is in a different taxonomic group to the ancestor.

Answer 39

An increase in taxonomic diversity that is caused by elevated rates of speciation that may be associated with an increase in morphological disparity.

Answer 40

A short period of geological time in which a high percentage of biodiversity, or distinct species died out.

Answer 41

Natural Selection QCAA Definition  Where the pressures of environmental selection confer a selective advantage on a specific phenotype to enhance its viability and fecundity. Alternate Definition  Certain characteristics you already have may become advantageous if the environment changes, leading to your survival and ability to reproduce. Natural selection is like genetic drift but with one major difference  It is not random.

Answer 42

There are two types of natural selection. 1. Positive Section which promotes the spread of beneficial alleles. Positive selection is selection that favours a heritable trait and the allele for that trait will increase within a population. 2. Negative Selection that hinders the spread of deleterious alleles. Negative selection is selection that disfavours a heritable trait meaning the alleles for that trait will decrease within the population.

Answer 43

Normal distribution: bell shaped trend Stabilising selection: culls extreme variations and narrows width of distribution Direction selection: favours one extreme and shifts distribution left/right Distruptive selection: favours both extremes and creates bimodal distribution

Answer 44

the genetic make-up of a population, includes the sum of all the alternative alleles for different genes present in a population.

Answer 45

Allele Frequency is the proportion of a particular allele in a population. * Range between 0-1 * An allele frequency of 0 means that no individuals in the population have the same allele. * An allele frequency of 1 mean all individuals have the allele and are homozygous for that allele. * The sum of alternative alleles for a given gene adds up to 1. * P + q = 1 - P = frequency of dominant allele. - Q = frequency of recessive allele.

Answer 46

is the exchange of alleles between populations because of migrating individuals who reproduce in new populations they join.

Answer 47

is when there is a change in allele frequencies in a population over generations because of chance alone. * No selection pressures appear to be acting on the phenotypes present. * Small, isolated populations are more suspectable to genetic drive.

Answer 48

The Bottleneck Effect – A sharp reduction in the size of a population is an extreme example of genetic drift often due to natural disasters, leaving behind a small, random assortment or survivors. - The frequency of some alleles in the population may this be reduced or limited.

Answer 49

The Founder Effect – When a small population of individuals is isolated and forms the basis of a new population. - A founder group of individuals may have limited variation, and my not be representative of the population from which it originates/ - After successive generations, the population is phenotypically diverse from its parents.

Answer 50

SPECIATION is the formation of a new distinct species during evolution. * Speciation and macroevolutionary changes result from an accumulation of microevolutionary changes. * Over a long period of time, evolution can result in speciation.

Answer 51

1) Divergent Evolution. * The process where groups from the same common ancestor evolve and accumulate differences, resulting in the formation of new species. * Adaptive radiation is a type of divergent evolution where there is rapid diversification of an ancestral population into several ecologically different species. * Evidence of divergent evolution is the pentadactyl limb. - This is a homologous feature that is found in chordates. - The basic structure is the same in all classes.

Answer 52

* The independent evolution of similar features in a species of different periods over time. * There is a problem when we can assume that certain animals are related, simply because they look similar. - E.g. bats, birds and insects all have wings but don’t have a common ancestor. - These structures are analogous. * Analogous structures arise because organisms live in similar environments and so have become adapted to that environment, not because they have ac common ancestor.

Answer 53

3) Parallel Evolution * The similar development of a trait in distinct species that are not closely related but share a similar original trait in response to evolutionary pressure. * E.g. the evolution of marsupials in Australia parallel the evolution of Placental mammals in other parts of the world.

Answer 54

4) Coevolution occurs when the influence of closely associated species have an effect on each other in their evolution. * Bees and pollen are a good example as the colour of plants wishing to be pollenated are of colours bees can see and therefore change depending on that.

Answer 55

When two populations of the same species become isolated from each other dur to geographic barriers

Answer 56

When two groups of the same geographic location evolve differently until they can no longer interbreed and are considered different species.

Answer 57

The populations that are diverging maintain a zone of contact and do not cease the exchange of genes completely. The species are spatially separated, but still exchange migrants meaning nothing is stopping the individuals from mixing and mating but it doesn’t happen.

Answer 58

Speciation occurs when a group of species separates from other members of its species and develops its own unique characteristics. For that to occur, the group needs to become isolated, and this can take place in different ways.

Answer 59

Geographic: populations of a species are divided by a geographic barrier such as a river, canyon, or mountain range (fragmentation and disasters) Spatial: Pretty much the same as geographic but on a larger scale. * Geographic and spatial usually lead to allopatric speciation and if pre-mating isolation is considered, sympatric speciation if the individuals are in the same area. Reproductive: Include mechanical isolation where copulation is attempted but transfer or sperm doesn’t take place (potential genital incompatibility, or females not recognising a mating dance. Temporal isolation can also take place when individuals do not mate because they are inactive or active at different times of day or during different seasons. * Reproductive and Temporal isolation usually result in parapatric speciation and are much more rare than geographical and spatial.

Unit 4 Flashcards

(84 cards)