Genetics Flashcards

Question

What is non-disjunction? (3)

Answer 1

1. A non-disjunction is an error in meiosis, where the chromosome pairs fail to split during cell division 2. It occurs in anaphase I where homologous pairs fail to split, or in anaphase II where the sister chromatids fail to split 3. As a result there will be too many or too few chromosomes in the final gamete cell (gamete would have 22 or 24 chromosomes - Down Syndrome)

Answer 2

1. Crossing over (in prophase I) 2. Random assortment of chromosomes (in metaphase I) 3. Random fusion of gametes from different parents

Answer 3

Meiosis I Replication prior to Crossing over during prophase I Homologous pairs line up randomly in metaphase I Homologous pairs are separated into chromosomes in anaphase I Meiosis II No replication No crossing over during prophase II Chromosomes line up randomly in metaphase II Chromosomes are separated into chromatids during anaphase II

Answer 4

The alleles of an organism/symbolic representation

Answer 5

The characteristic or trait of an organism (Brown eyes or blue eyes, etc)

Answer 6

Dominant allele: an allele that has the same effect on the phenotype whether it is present in the homozygous or heterozygous state. Recessive allele: an allele that only has an effect on the phenotype when present in the homozygous state.

Answer 7

Pairs of alleles that both affect the phenotype when present in a heterozygote.

Answer 8

Through performing experiments on a variety of different pea plants, Mendel established: 1. Law of Segregation: When gametes form, alleles are separated so that each gamete carries only one allele for each gene 2. Law of Independent Assortment: The segregation of alleles for one gene occurs independently to that of any other gene* 3. Principle of Dominance: Recessive alleles will be masked by dominant alleles†

Answer 9

``` Phenotype Genotype A IAIA or IAi B IBIB or IBi AB IAIB O ii ```

Answer 10

1. Sex linkage refers to when a gene controlling a characteristic is located on a sex chromosome (X or Y) 2. Since the Y chromosome is shorter than the X chromosome, sex-linked conditions are usually X-linked as very few genes exist on the shorter 3. • X-linked recessive diseases such as colour blindness and hemophilia are more common in males because they only carry one X chromosome, therefore if they inherit the X chromosome with the disease, they will also have the disease 4. This also means that males can only pass these alleles onto their daughters as their sons only receive the Y chromosome

Answer 11

Mutations can be spontaneous (caused by copying errors during DNA replication), or induced by exposure to external elements. Factors that can include mutations include: o Radiation: UV Radiation from the sun, gamma radiation from radioisotopes, X-rays from medical equipment o Chemical: Reactive oxygen species, alkylating agents (found in cigarettes) o Biological Agents: Bacteria, viruses

Answer 12

Polymerase chain reaction is used to copy and amplify minute quantities of DNA. It can be useful when only a small amount of DNA is available but a large amount is required to undergo testing. PCR occurs in a thermal cycler and involves a repeat procedure of 3 steps: 1. Denaturation – DNA sample is heated to separate it into two single strands (~95ºC for 1 min) 2. Annealing – DNA primers attach to the 3’ ends of the target sequence (~55ºC for 1 min) 3. Elongation – A heat-tolerant DNA polymerase (Taq) binds to the primer and copies the strand (~72ºC for 2 min)

Answer 13

Separate fragments of DNA are moved through an electric field in order to create a DNA profile. 1. Enzymes cut DNA into different sized fragments 2. The DNA sample is placed at one end of the porous gel 3. This side of the gel with the DNA sample is exposed to a negative electrical current 4. The DNA fragments move through the gel and stop at different points, creating a band 5. The bands are dyed so we can see them Affected by charge and size

Answer 14

DNA profiling is a technique where individuals can be identified and compared via their DNA profiles 1. Restriction enzymes are used to break DNA into small fragments 2. Fragments are subjected to electrophoresis 3. Portions of DNA placed on gel 4. Electric field/Voltage applied 5. Negatively charged portions of DNA migrate to positive electrode 6. DNA portions separated by size/small portions of DNA travel further through the gel 7. DNA sequences stained 8. Observed under UV light

Answer 15

o Establishing paternity o Comparing DNA at a crime scene with potential suspects o Released prisoners that are wrongly convicted o Identifying people who died last century o Establishing relationships in populations to determine migrating patterns of evolutionary relationships

Answer 16

Gene transfer: Taking a gene from one organism and placing it into another organism

Answer 17

1. Isolation of gene and vector (by PCR and centrifugation) 2. Digestion of gene and vector (by restriction endonuclease, creating sticky/blunt ends) 3. Ligation of gene and vector (by DNA ligase) 4. Selection and expression of transgenic construct

Answer 18

Clones are groups of genetically identical organisms, derived from a single original parent cell.

Answer 19

An organism with a gene that has been artificially inserted into its genome (done by gene modification) e.g. golden rice (beta carotene-> Vitamin A), cold tolerant tomatoes (artic fish)

Answer 20

Benefits 1. Pest-resistant crops can be made. Therefore less spraying of pesticides 2. Longer shelf-life therefore less spoilage Risks: 1. Non-target organisms can be affected 2. GMOs reduces biodiversity

Answer 21

Benefits 1. Nutritional value of food improved by increasing nutrient content 2. Crops could be produced that lack toxins or alleges Risks 1. Proteins from transferred genes could be toxic or cause allergic reactions 2. Antibiotic resistance genes used as markers during gene transfer could spread to bacteria

Answer 22

Reproductive cloning was first done in 1996 when Dolly the sheep was cloned 1. A somatic cell from the original sheep was collected and the nucleus (and therefore the DNA was removed) 2. A donor egg from another sheep was collected and all of the DNA was removed from the egg 3. The DNA from the donor sheep was placed inn the empty egg 4. The embryo was placed in the uterus of a surrogate sheep 5. The embryo developed and Dolly the shape was born who was an exact copy

Answer 23

Making one type of cell to replace damaged cells in the body using undifferentiated cells

Answer 24

1. The parent organism divides equally in two, so as to produce two genetically identical daughter organisms 2. This method of cloning occurs in Planaria (flatworms) but is also common to bacteria and protists (e.g. euglena, amoeba)

Answer 25

1. Cells split off the parent organism, generating a smaller daughter organism which eventually separates from the parent 2. This method of cloning occurs in Hydra but is also common to many species of yeast

Answer 26

1. New organisms grow from a separated fragment of the parent organism 2. This method of cloning is common to starfish and certain species of annelid worms

Answer 27

1. Embryos are formed from unfertilised ova (via the production of a diploid egg cells by the female) 2. This method of cloning occurs in certain species of insect, fish, amphibians and reptiles

Genetics Flashcards

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