Inheritance

Question 1

what is a gene

Answer 1

a DNA sequence that codes for a specific polypeptide

Question 2

what is a locus

Answer 2

location of a gene on a chromosome

Question 3

what is a chromosome

Answer 3

long peice of dna containing many genes

Question 4

what are alleles

Answer 4

slight variations of genes that result in a slightly different polypeptide being formed

Question 5

what are homologous chromosomes

Answer 5

each chromosome has a copy of it, this can be exactley the same or a different allele

Homologous is exactley the same
heterozygous means one is an allele

Question 6

what is the phenotype

Answer 6

the observable charicteristics, determined by the genotype and environment

Question 7

what is a dominant allele

Answer 7

allele that ios always expressed if it is present

Question 8

recessive allele

Answer 8

only expressed if it is homolygous

Question 9

what is codominance

Answer 9

when both alleles in a heterozygous genotype are equally expressed

Question 10

what is linkage

Answer 10

refers to genes that are inherited together as they are on the same chromosome

Question 11

what is sex linkage

Answer 11

sex linked genes are those expressed on the X chromosome ONLY

Question 12

why are males more likely to express reccessive sex linked traits

Answer 12

only have one x allele so just that one needs to be reccesive as no genes are ever linked to the Y chromosome

Question 13

what is autosomal linkage

Answer 13

occurs on the autosomes (chromosomes that are not sex chromosomes)

2 or more genes on a chromosome dont independantly assort during meiosis so are linked and remain together in the original parental combination

Question 14

is the chance of each allele being passed on during gamete formation equal

Answer 14

yes

Question 15

how do we repersent codominant alleles in a punnet square

Answer 15

gene in capital letter with small allele letter above eg. IAIA

Question 16

how do we repersent sex linked alleles in a punnet square

Answer 16

similar to codominance however we use chromosomes X or Y as the capital letter

Question 17

function of monohybrid crosses

Answer 17

track inheritance of one gene

Question 18

function of dihybrid crosses

Answer 18

track inheritance of 2 genes simultaneously

Question 19

what is the genetic notation for dihybrid crosses

Answer 19

write both alleles first then both alleles of the second gene

Example: for genes with alleles Y/y and G/g, a correct genotype is YyGg

DO NOT MIX THEM Eg. avoid YGyg

Question 20

what is assumed in dihybrid cross predictions

Answer 20

independant assortment of genes

Question 21

linked genes are inherited together

Answer 21

affecting expected offspring ratios, reducing variation

Question 22

what is the correct notation for linked genes

Answer 22

linked alleles are often written in brackets to show they are inherited together

eg. (FG)(FG) instead of FFGG

Question 23

what is epistasis

Answer 23

when one gene affects the expression of another gene

Question 24

how does epistasis occur

Answer 24

involving 2 genes on different chromosomes influencing the same trait

the interaction between these alleles determines the resulting phenotype

Question 25

what is a test cross used for

Answer 25

deducing the genotype of an unknown individual that is expressing a dominant phenotype

Question 26

what do we do in a test cross

Answer 26

we cross the person whose genotype we are trying to discover with an individual with a recessive phenotype

Question 27

how do we analyse these results for a monohybrid test cross

Answer 27

if there is no recessive phenotype in the offspring then the individual is homozygous dominant If there is at least one recessive phenotype in the offspring → The individual is heterozygous

Question 28

how do we analyse the results of a test cross for dihybrids

Answer 28

If there are no recessive phenotypes (for either gene) → The unknown is homozygous dominant for both genes If there is at least one recessive phenotype for one gene only → The unknown is heterozygous for one gene and homozygous dominant for the other If there is at least one recessive phenotype for both genes → The unknown is heterozygous for both genes

Question 29

function of genetic diagrams

Answer 29

predicting offspring genotypes and phenotypes using known parental genotypes

Question 30

why are genetic diagrams not always accurate

Answer 30

it is estimated on probability and actuial offspring can differ due to random fertilisation of gametes.

Question 31

how are genetic diagram predictions expressed

Answer 31

shown as ratios

Question 32

function of the chi squared test

Answer 32

determine whether or not there is a significant difference between the observed and expected results in an experiment

Question 33

chi squared value formula

Answer 33

χ² = Σ((O - E)² / E), where O represents the observed frequencies and E represents the expected frequencies.

Question 34

what is a critical value

Answer 34

depends on the probability level used and the degrees of freedom

Question 35

how to compare chi to critical

Answer 35

is critical value or chi larger

Question 36

if critical value is larger

Answer 36

there is no significant difference and this is due to chance - we can assume there is no correlation between these data

Question 37

if chi is larger

Answer 37

there is a significant difference and this is not due to chance - we can assume there is a correlation between these data