Topic 3 – Genetics-Inheritance

Question 1

what is a chromosome?

Answer 1

a long coiled molecule of DNA that carry genetic information in the form of genes

Question 2

define gene

Answer 2

section of DNA that codes for specific sequence of amino acids which undergo polymerization to form a protein

Question 3

what are alleles?

Answer 3

different versions of same gene

Question 4

define genotype

Answer 4

organism genetic composition, describes all alleles

Question 5

define phenotype

Answer 5

organism observable characteristics due to interactions of genotype and environment

Question 6

define homozygous

Answer 6

having 2 identical alleles FF or ff

Question 7

define hetrozygous

Answer 7

having 2 different alleles Ff

Question 8

what is a dominant allele?

Answer 8

describes allele that is always expressed, represented with capital letter F

Question 9

what is a recessive allele?

Answer 9

allele that is only expressed in absence of dominant allele

represented with a small letter e.g. f

Question 10

what is monohybrid inheritance?

Answer 10

inheritance of a single gene

Question 11

what is the problem with single gene crosses?

Answer 11

most characteristics are controlled by multiple alleles rather then one

Question 12

what are sex chromosomes?

Answer 12

pair of chromosomes that determine sex
males have X and a Y chromosome
females have two X chromosomes.

Question 13

why does the inheritance of Y chromosome mean embryo develops into a male?

Answer 13

testes development in embryo is stimulated by a gene present of Y chromosome

Question 14

other then a punnett square, how else monohybrid inheritance be represented?

Answer 14

using family pedigree

Question 15

what is a sex linked characteristic?

Answer 15

a characteristic that is coded for by an allele found on sex chromosome

Question 16

why are majority of genes found on X chromosome rather then Y?

Answer 16

X chromosome is bigger then Y, so more genes are carried on it

Question 17

why are men most likely to show phenotype for a recessive sex linked trait then wommen?

Answer 17

many genes are found on X chromosome that have no counterpart on Y chromosome.
Women have 2 alleles for each sex linked gene whereas men often have 1, so only 1 recessive allele is required to produce recessive phenotype in males

Question 18

give an example of a characteristic that is determined by more then 1 allele?

Answer 18

blood groups is determined by 3 alleles: Ia Ib Io

Question 19

Name 4 different blood groups

Answer 19

A, B, AB, O

Question 20

what are codominant alleles?

Answer 20

alleles that equally contribute to organism phenotype. expressed to equal extent.

Question 21

describe codominance in blood groups

Answer 21

IA and IB are codominant

IA IB gives blood group AB

Question 22

Why does IA IO give blood group A?

Answer 22

Io is recessive to IA

IA is dominant and expressed given to blood group A

Question 23

what are possible genotypes for B?

Answer 23

Ib or Io

Ib or Ib

Question 24

what is genotype for blood group O?

Answer 24

Io Io