Extending Mendel's Laws - Genetics

Question 1

define recombination frequency

Answer 1

percentage of times that a crossover occurs as gametes are formed

Question 2

what is the gene-chromosome theory

Answer 2

that genes exist at specific sites arrange in a linear manner along chromosomes

Question 3

true or false: with multiple allele inheritance, any given individual has more then two alleles for each gene

Answer 3

false; any given individual organism has only two alleles for each gene but many different alleles exist for the trait within the population as a whole

Question 4

true or false: crossing over occurs at different probabilities based on its point on the sister chromatid

Answer 4

false; crossing over occurs with equal probability at nearly any point on the sister chromatids except near the centromere

Question 5

why are sex-linked traits expressed in different ratios by male and female offspring

Answer 5

because they are governed by the segregation of X and Y chromosomes

Question 6

what is the concept of crossing over used for in chromosome mapping

Answer 6

the relative positions of genes on a chromosome

Question 7

why are males more likely to be affected by sex linked traits

Answer 7

because they only have 1 X chromosome so they either have the trait or they dont, they can not be carriers

Question 8

true or false: continuous traits are controlled by one gene

Answer 8

false; they are usually controlled by more than one gene

Question 9

how many map units is 10%

Answer 9

10 map units –> 1% = 1 map unit

Question 10

Who studied fruit flies after sutton and ended up further proving Sutton’s theory

Answer 10

thomas hunt morgan

Question 11

is a persons blood type a genotype or phenotype

Answer 11

the blood type of an individual is a phenotype

Question 12

do linked genes segregate independently

Answer 12

no

Question 13

who discovered the first gene to be mapped to a specific chromosome and when

Answer 13

thomas morgan in 1910

Question 14

can females be carriers of a y-linked trait

Answer 14

no

Question 15

define sex linked traits

Answer 15

a trait controlled by genes on either the X or Y chromosomes

Question 16

why is blood type an example of multiple alleles

Answer 16

because there are 3 different alleles (IA, IB, and i) which combine to produce 4 different blood types but each person only has 2 of the 3 alleles

Question 17

how is the probability of recombination of linked genes determined

Answer 17

by the relative position of the alleles on the chromosome

Question 18

whats the formula for calculating recombination frequency

Answer 18

recombination frequency = (number of recombinant types)/(total number of offspring) x 100%

Question 19

can you place continuous traits into discrete categories

Answer 19

no; they vary over a continuum instead of a yes or no category

Question 20

what are linked genes

Answer 20

genes found on the same chromosome

Question 21

true or false: the X chromosome in a cell that is inactive is chosen at random

Answer 21

true

Question 22

when does crossing over occur

Answer 22

prophase I of meiosis

Question 23

define crossing over

Answer 23

the process by which non-sister chromatids exchange genes during prophase I of meiosis, allowing for the recombination of genes

Question 24

define polygene

Answer 24

a group of genes that all contribute to the same trait

Question 25

what did alfred sturtevant discover

Answer 25

that the frequency of linked gene separation could be explained by assigning each gene a specific position along a linear chromosome

Question 26

true or false: crossing over is a random event

Answer 26

true

Question 27

what happens to the X chromosomes in every female cell

Answer 27

one of the X chromosomes will be unactive in every female cell

Question 28

in two genes, where will the alleles be at the point which a crossover occurs

Answer 28

on seperate chromosomes and will therefore migrate into different gametes

Question 29

what is a common example of multiple alleles in humans

Answer 29

blood type

Question 30

how do you notate sex linked traits

Answer 30

by putting the allele letters as superscripts above the X chromosome letter, ensuring that you never write an allele above the Y chromosome letter

Question 31

define multiple alleles

Answer 31

a pattern of inheritance in which a gene has more than two alleles for any given trait

Question 32

true or false: environmental conditions have no affect over the expression of genetic traits

Answer 32

false; environmental conditions often affect the expression of a genetic trait

Question 33

whats an example of a continuous trait

Answer 33

human height

Question 34

define continuous traits

Answer 34

a trait for which the phenotypes vary gradually from one extreme to the other

Question 35

what ischromosome mapping

Answer 35

a process for determining the relative position of genes on a chromosome

Question 36

how do you write blood alleles

Answer 36

capital i (I) with an A or B superscript for a dominant allele and lowercase i (i) for the recessive allele

Question 37

define parental types

Answer 37

offspring that have chromosomes that are identical to those of their parents

Question 38

whats another name for recombinant types

Answer 38

recombinants

Question 39

true or false: there are more Y-linked sex traits then X-linked

Answer 39

false; there are relatively few y-linked traits

Question 40

define polygenic trait

Answer 40

a trait that is controlled by more than one gene

Question 41

whats a map unit

Answer 41

the distance between points on a chromosome where a crossover is likely to occur

Question 42

what is an example of an x-linked trait

Answer 42

colorblindness -> result of a recessive trait that is carried on the X chromosome

Question 43

why can females carry 2 X chromosomes and males only 1 without a difference in the expression of X-linked traits and without any harm from having 2 of the same chromosome

Answer 43

because every cell only has 1 functioning X chromosome

Question 44

define recombinant types

Answer 44

offspring that have a different combination of alleles than the chromosomes of their parents

Question 45

what is a barr body

Answer 45

a structure formed when the inactive X chromosome condenses tightly

Question 46

how are y-linked traits passed

Answer 46

only from males to their sons

Question 47

what is the percentage of recombinant types in the F1 generation directly proportional to

Answer 47

the distance between genes

Question 48

what did Morgan find regarding the seperation of linked genes

Answer 48

that they would seperate with a predictable frequency and that this frequency varied among different pairs of linked genes

Question 49

what does the process of crossing over allow

Answer 49

two genes on the same chromosome to be found in different gametes

Question 50

define order of dominance

Answer 50

sequence indicating which alleles are dominant over other alleles

Question 51

whats map distance

Answer 51

the distance between genes on a single chromosome

Question 52

where is a crossover more likely to occur

Answer 52

between genes that are farther apart on a chromosome