Full Study Guide Flashcards
(28 cards)
Differences between meiosis and mitosis
Mitosis produces two genetically identical “daughter” cells from a single “parent” cell.
Meiosis produces cells that are genetically unique from the parent and contain on half as much DNA. Single cell divides twice to produce 4 cells, which only contains half as much DNA.
Similarities between meiosis and mitosis
Produce new cells; similar basic steps; start with a single parent cell
How does meiosis explain the first law of Mendel?
The Law of Equal Segregation, which states: during gamete formation, the two alleles at a gene locus segregate from each other; each gamete has an equal probability of containing either allele.
What is crossover? When does it happen? What are the consequences?
Crossover: the exchange of DNA between paired homologous chromosomes (one from each parent) that occurs during the development of egg and sperm cells (meiosis).
Happens during meiosis when chromosomes of the same type are lined up.
New combinations of alleles in the gametes (egg or sperm) formed
What happens when there are errors in meiosis?
Errors can occur during meiosis producing gametes with an extra or missing chromosome. The consequences of this following fertilization depend on which chromosomes are affected. Often the embryo is not viable, but some of these errors can lead to trisomy conditions or sex chromosome disorders.
What is Mendel’s second law? What do you expect if you cross two heterozygous individuals for two genes, assuming this law is correct.
Mendel’s Second Law - the law of independent assortment; during gamete formation the segregation of the alleles of one allelic pair is independent of the segregation of the alleles of another allelic pair.
9:3:3:1
How Mendel’s second law relate to the meiosis?
Explains how two or more different traits separate from each other during sexual reproduction. It states that a heterozygous trait (Rr) will separate during meiosis into R and r as possible gametes.
What are the causes of unexpected rations and why?
Non-dominant nature of traits, several genes affecting the trait, environmental effects, incomplete penetrance, lethal phenotypes
What are allelic series? How they differ from multiple genes affecting a single trait?
Allelic Series: describes different mutant alleles of a gene that cause a range of phenotypes, whereby each one carries a single point mutation within different regions of the same gene.
Multiple alleles follow complete dominance or codominance while polygenic traits follow codominance or incomplete dominance
How dominance occurs in allelic series? Do we have a general for all allelic series? How can we make assumptions about dominance?
Depends on the relative influence of each allele for a specific phenotype under certain environmental conditions
How gene interaction can cause distortion of the 9:3:3:1 ratios?
Epistatic interactions: describe some form of statistical interaction between genetic factors and is alternatively sometimes used to describe instances in which the effect of a particular genetic variant is masked by a variant at another locus.
Incomplete Penetrance
form of penetrance in which not all individuals carrying a deleterious gene express the associated trait or condition
Variable expressibility
the range of signs and symptoms that can occur in different people with the same genetic condition.
Pleiotropy
the production by a single gene of two or more apparently unrelated effects.
What happens when genes are located close to each other in a chromosome?
Genes that are sufficiently close together on a chromosome will tend to “stick together,” and the versions (alleles) of those genes that are together on a chromosome will tend to be inherited as a pair more often than not. This phenomenon is called genetic linkage.
What is the relationship between the proximity of two genes and their inheritance?
The closer two genes were to one another on a chromosome, the greater their chance of being inherited together. In contrast, genes located farther away from one another on the same chromosome were more likely to be separated during recombination.
What is the relationship between genes located in different chromosomes?
Genes on separate chromosomes are never linked
What are parental and recombinant chromosomes?
The chromosomes that are similar to their parents are referred to as parental chromosomes. The chromosomes that are different from their parents are referred to as recombinant chromosomes
What is the maximum recombination rate between two genes? Why?
50 percent
Random assortment of genes generates 50% recombination (non-linked genes produce 1:1 parental to non-parental. Thus, the recombination frequency would be non-parental/total → 1/(1+1) = 50%)
How map units/centiMorgans relate to the recombination rate?
The # of recombinant offspring / total # of offspring x 100% = recombination frequency; Recombination frequency = map units = centiMorgan
How to build a genetic map? What is necessary? How does it relate to the physical distance?
Step 1: Start with the genes that are the farthest apart first: B and C are 45 map units apart and would be placed far apart.
Step 2: Solve it like a puzzle, using a pencil to determine the positions of the other genes.
Step 3: Subtraction will be necessary to determine the final distances between each gene.
How close they are on the chromosome and how closely linked they are.
If I have 3 genes and want to learn their distance in cM, how many types of crosses do I need? Why?
https://www.ndsu.edu/pubweb/~mcclean/plsc431/linkage/linkage3.htm
What are double crossovers? Are they common?
A double crossover occurs when fragments of the chromosome are exchanged in two places. The result of a double crossover is that the two ends of the chromosome are parental, but a region between the crossovers has been “swapped” for another sister chromatid sequence
Not common
What is the expected frequency of each genotype if the genes are linked? How do I test if my hypothesis is correct?
Chi Square Test
