inheritance 2

Question 1

Genotype:

Answer 1

The genetic constitution of an organism

(the alleles it has for a gene).

Question 2

Phenotype

Answer 2

The expression of the genes and its interaction with the environment.

Question 3

Homozygous

Answer 3

A pair of homologous chromosomes carrying the same alleles for a single gene.

Question 4

Heterozygous

Answer 4

A pair of homologous chromosomes carrying two different alleles for a single gene.

Question 5

Recessive allele:

Answer 5

An allele that is only expressed if there is no dominant allele present.

Question 6

Dominant allele:

Answer 6

An allele that will always be expressed in the phenotype.

Question 7

Codominant:

Answer 7

Both alleles are equally dominant and are both expressed in the phenotype.

Question 8

Multiple Alleles

Answer 8

More than two alleles for a single gene.

Question 9

Sex-linkage

Answer 9

A gene whose locus is on the X chromosome

Question 10

Autosomal Linkage:

Answer 10

Genes that are located on the same chromosome (not the sex chromosomes).

Question 11

Epistasis:

Answer 11

When one gene modifies or masks the expression of a different gene at a different locus.

e.g. colour of coat of animal

Question 12

Monohybrid

Answer 12

Genetic inheritance cross of a characteristic determined by one gene.

Question 13

Dihybrid:

Answer 13

Genetic inheritance cross for a characteristic determined by two genes.

Question 14

gene

Answer 14

small section of DNA which codes for a polypeptide

Question 15

Alleles

Answer 15

alternative form of a gene

Question 16

Monohyrid genetic diagram coding

Answer 16

single letter

capital or lower case

e.g.

B or b

Question 17

codominant diagram coding

Answer 17

Gene^ allele

Question 18

multiple alleles diagram coding

Answer 18

gene^ allele

Question 19

sex linkage diagram coding

Answer 19

chromosome^ alleles

Question 20

autosomal linkage diagram coding

Answer 20

single letter, capital or lower case

Aa Bb

Question 21

Epistasis diagram coding

Answer 21

single letter, capital or lower case

Question 22

Answer 22

monohybrid inheritance

1- parent genotype (any letter) =

2- punnret Square =

3- probabilities

Question 23

Answer 23

codominant inheritance

Question 24

blood groups

Answer 24

A dominant - homo or hetero
B Dominat - homo or heter
AB - codominant
O - recessive

Question 25

Answer 25

Question 26

Answer 26

sex linkage - gene only on X chromosome

Question 27

if more than 2 phenotypes

Answer 27

either codominace and or multiple allele inheritances

Question 28

Dihybrid cross example

Answer 28

use a genetic cross

Question 29

in a genetic crosses you must show:

Answer 29

1- parental phenotype 2- parental genotype 3- possible gametes 4- offspring genotype 5- offspring phenotype 6- probably of each phenotype

Question 30

Answer 30

3- possible gametes RY, Ry, rY, ry RY Ry rY ry 4- offspring genotype - big punnet square

Question 31

in dihybrid cross if two heterozygous parents cross what is the ratio you alway get

Answer 31

9:3:3:1

Question 32

Crossing over

Answer 32

new combination of alleles in the gametes - predicted gametes in punnet square may differ

Question 33

Autosomal linkage with two heterozygous parents ratio

Answer 33

3:1

Question 34

if you don't observe the ratio you expect...

Answer 34

crossing over has occurred

Question 35

Epistasis diagram Qs

Answer 35

Question 36

Expected offspring phenotype ratio for heterozygous monohybrid cross

Answer 36

3:1

Question 37

What sex chromosomes do female humans have

Answer 37

XX

Question 38

What sex chromosomes do male humans have

Answer 38

XY

Question 39

Where are sex-linked genes located

Answer 39

Non-homologous section of the X chromosome

Question 40

Why are males more likely to show recessive sex-linked characteristics than females

Answer 40

Chromosomes are homologous in females Male has one allele for sex gene Recessive allele is always expressed in males Females need two recessive alleles for allele to be expressed

Question 41

Why do X and Y chromosomes not form a typical bivalent

Answer 41

X and Y chromosomes are different sizes Chromatids are unable to line up and form bivalent Short pairing reigon means most of length not homologous

Question 42

What does it mean when p < 0.05 in a chi-squared test

Answer 42

Reject the null hypothesis Is a significant difference btween the observed and expected values

Question 43

What does it mean when p > 0.05 in a chi-squared test

Answer 43

Accept the null hypothesis There is no significant difference between the observed and expected values

Question 44

What reasons are there for why the observed phenotypic ratios are not the same as expected ones

Answer 44

Lethal genotypes / lethal alleles Epistasis Random fertilisation of gametes Small populations

Question 45

How are gametes with different combinations of alleles created from autosomally linked parents

Answer 45

Crossing-over of chromatids

Question 46

What are the criteria for the chi squared test

Answer 46

data placed in discrete categories Large sample size Only raw count data allowed no data values equal zero

Question 47

locus

Answer 47

position of gene on a particular DNA molecule

Question 48

Chi squared equation

Answer 48

X^2 = sum of (O -E )^2 / E

Question 49

degrees of freedom

Answer 49

n-1

Question 50

characteristics are determined by

Answer 50

genes

Question 51

In fruit flies, males have the sex chromosomes XY and the females have XX. In fruit flies, a gene for eye colour is carried on the X chromosome. The allele for red eyes, R, is dominant to the allele for white eyes, r. (a) Male fruit flies are more likely than female fruit flies to have white eyes. Explain why.

Answer 51

males have one allele Female need two recessive alleles females are homozygous recessive female could have dominated and recessive alleles

Question 52

The scientists tested their null hypothesis using the chi-squared statistical test. After 1 cycle their calculated chi-squared value was 350 The critical value at P=0.05 is 3.841 What does this result suggest about the difference between the observed and expected results and what can the scientists therefore conclude?

Answer 52

1- There is a less than 0.05/5% probability that the difference(s) (between observed and expected) occurred by chance; 2- Calculated value is greater than critical value so the null hypothesis can be rejected; 3- (The scientists can conclude that) the proportion of plants that produce 2n gametes does change from one breeding cycle to the next;