Genetics & Inheritance

Question 1

dominant gene

Answer 1

an allele that masks the effect of an another

Question 2

recessive gene

Answer 2

an allele that is masked by the alternative (dominant)

Question 3

gene

Answer 3

the factor that determines an inherited characteristic, located in chromosomes

Question 4

allele

Answer 4

an alternative form of a gene

Question 5

progeny

Answer 5

offspring

Question 6

principle of segregation

Answer 6

the principle that the alleles for a trait are separated during the formation of gametes

Question 7

monohybrid cross

Answer 7

a mating between individuals in which only one pair of contrasting alleles is being considered

Question 8

homozygous

Answer 8

a.k.a. pure-breeding
individual has same alleles for particular characteristic

Question 9

heterozygous

Answer 9

a.k.a. hybrid
individual has 2 different alleles for particular characteristic

Question 10

phenotype

Answer 10

physical appearance of an individual determined by the expression of the alleles for that characteristic

Question 11

genotype

Answer 11

the genetic make-up of an individual determined by the alleles for the characteristic being considered

Question 12

first filial generation

f1

Answer 12

offspring of the first set of parents

Question 13

second filial generation

f2

Answer 13

offspring from crossing the first filial generation

Question 14

loci/locus

Answer 14

part of the chromosome where that gene is located

Question 15

What did Gregor Mendel establish

2

Answer 15

• the various hereditary characteristics were controlled by factors (genes) that occurred in pairs
• during the formation of the gametes, the pairs of each factors seperate and each gamete receives only one set of factors with the other set going to the other gamete

not codominance or incomplete dominance!

Question 16

Pedigree

Answer 16

a symbolic family tree showing males and females and those individuals that have a particular characteristic or disease

Question 17

Autosomal

Answer 17

concerned with non-sex chromosomes

Question 18

punnet square

Answer 18

predicts the probability of the genotype & phenotype of the offspring

Question 19

codominance

2

Answer 19

two or more alleles are equally dominant
both phenotypes are expressed

e.g. I^A & I^a

Question 20

multiple alleles

Answer 20

more than 2 alleles for a specific characteristic
e.g. blood groups

Question 21

genetic counselling

Answer 21

advice regarding the risks of genetic disorders in future children

Question 22

Red-green colour blindness

2

Answer 22

• X-linked recessive
• Lack the ability to discriminate between the colours green and red.

Question 23

Haeomophilia

3

Answer 23

• X-linked recessive
• The blood clots very slowly or not at all.
• Prominent in the royal families that descended from Queen Victoria

Question 24

Phenylketonuria

2

Answer 24

• Autosomal recessive
• Can not produce the enzyme needed to break down phenylalanine which then accumulates, causing brain deformities and mental retardation.

Question 25

Huntington's disease | 2 ## Footnote just description

Answer 25

- autosomal dominant - usually appears after 40 years of age

Question 26

Huntington's Disease symptoms | 4

Answer 26

- characterised by the occasional involuntary flailing movements of arms and legs - difficulty voluntarily moving limbs - writhing hand, head, trunk and feet movements - progressive loss of the ability to think clearly (dementia)

Question 27

if autosomal recessive on petigree | 2

Answer 27

- unaffected parents have affected offspring - both affected parents have affected offspring

Question 28

if x-linked dominant on petigree

Answer 28

if male is affected -> both mother and daughters are affected

Question 29

if x-linked recessive on petigree

Answer 29

if female is affected -> her sons and father are affected

Question 30

incomplete dominance

Answer 30

neither allele is dominant fully over the other resulting in a blended phenotype