inheritance

Question 1

what the genotype

Answer 1

genetic constitution of an organism

Question 2

what is the phenotype

Answer 2

the expression of this genetic constitution and its interaction with the environment
eg. brown eyes

Question 3

what is an allele

Answer 3

different versions of a gene

Question 4

what is homozygous

Answer 4

both alleles at a specific locus on each homologous chromosome are the same
eg. BB or bb

Question 5

what is heterozygous

Answer 5

both alleles at a specific locus on each homologous chromosome are different
eg. Bb

Question 6

what is a dominant allele

Answer 6

in heterozygous it is the allele that is expressed in the phenotype

Question 7

what is a recessive allele

Answer 7

in heterozygous state it’s the allele that isn’t expressed in the phenotype
only expressed if homologous recessive

Question 8

what is a codominant allele

Answer 8

both alleles for same gene in heterozygous organism contribute to the phenotype

Question 9

what should genetic inheritance diagrams contain

Answer 9

parent genotype
parent phenotype
parent gamete genotype
punnet square
offspring genotypes labelled with phenotypes

Question 10

what is monogenetic inheritance

Answer 10

inheritance of characteristics controlled by a single gene

Question 11

draw a mono hybrid cross from inheritance of wind length in fruit flies

N - normal wings
n - little wings

homozygous dominant parent and homozygous recessive parent

f1 and f2 generations

Answer 11

parent 1 - NN
parent 2- nn
f1- N. N
n Nn Nn
n Nn Nn
all Nn heterozygous

parent 1- N n
parent 2 N n
N. n
N NN. Nn
n. Nn nn
3:1 ratio homo to hetro
normal wings: vestigial wings

Question 12

what is dihybrid

Answer 12

inheritance is two different characteristics controlled by two different genes

an allele from one pair of chromosomes can entered a gamete with either allele from the other pair of independent segregation so
AaBb can produce gamete AB Ab aB ab

Question 13

what do crosses involving codominace involve

Answer 13

both alleles in a heterozygous individual contribute to phenotype

eg. coat colour in cattle
red and white allele = roan coat - speckled white and red coat

Question 14

what do multiple allele crosses involve

Answer 14

individuals only have 2 alleles die a gene but there may be more than 2 alleles
there is usually a dominance hierarchy

Question 15

what do sex linkage crosses involve

Answer 15

a gene is sex linked ur it’s locus is in a sex chromosome
specific characteristics more likely to be inherited in either female or male offspring
genes are more likely to be X linked

females have tow copies of gene (XX)
- only express recessive if homozygous recessive
males have one copy of gene (XY)
- can’t be heterozygous, express recessive X linked allele is only one copy present

Question 16

what do autosomal linkage crosses involve

Answer 16

two genes carried on same autosome

genes stay together during independent segregation so assuming no crossing over all linked genes remain together during meiosis
therefore linked genes pass into gametes together
higher proportion of offspring will have parents genotype and phenotype

Question 17

draw a pair of chromosomes autosomally linked with Tr and tR vs a pair of chromosomes not autosomally linked

Answer 17

T | T t | t
| |
r. | r R |. R
Tr. tR

Question 18

what is epistasis

Answer 18

interaction of non linked genes where one masks the expression of the other

Question 19

give an example of epistasis in mice

Answer 19

A - dominant albino
a - recessive black

B - dominant production of melanin
b- recessive no production of melanin leads to white

Question 20

draw a genetic cross of an agglutination homozygous dominant mice and a white homozygous recessive mouse

Answer 20

AB. Ab. aB. ab
AB
Ab
aB
ab
9 brown agouti: 4 albino :3 black

Question 21

what is chi squared test

Answer 21

stats test to find whether the difference between expected and observed data is due to chance

Question 22

when to use a chi squared test

Answer 22

the data is in categories
the data is frequency

Question 23

how would you carry out a chi squared test

Answer 23

1. define null hypothesis
   - there is no significant difference between… any difference i’d use to chance
2. calculate chi squared
3. determine degrees of freedom ( categories -1)
4. determine critical value at p = 0.05
5. interpret results - value has to be equal to or larger than critical value