MGD 8- genotype & phenotype: patterns of inheritance

Question 1

where are genes and proteins located? sequence of how proteins are made?

Answer 1

genes: on chromosomes in nucleus
proteins: in cytoplasm
DNA –> RNA –> AA –> polypeptide chains of protein
genotypes determine phenotypes

Question 2

what are the environmental factors that can affect genotypes and phenotypes?

Answer 2

radiation, mutagens, chemicals that affect cell growth, diet, lifestyle

Question 3

what are the 2 methods that genetics can change via?

Answer 3

inheritance and variation

each individual has 2 alleles of same gene

Question 4

homozygous definition

Answer 4

2 alleles of a gene are the same (individual is a homozygote)

Question 5

heterozygous

Answer 5

2 alleles of a gene are different (individual is a heterozygote)

Question 6

hemizygous

Answer 6

only 1 allele of a gene on the X chromosome (i.e. males only) - the other is Y so gene isn’t present

Question 7

dominant

Answer 7

the dominant allele of heterozygote determines the phenotype

Question 8

recessive

Answer 8

the non-dominant allele of heterozygote is called recessive

require both alleles to be recessive to express the phenotype

Question 9

what are the different types of inheritance possible?

Answer 9

autosomal VS sex-linked:
autosomal recessive
autosomal dominant
X-linked recessive
X-linked dominant
Y-linked

Question 10

describe inheritance of autosomal recessive and an example of a disease which is autosomal recessive

Answer 10

heterozygotes unaffected
males & females equally affected
2 heterozygotes have a 25% of having an affected offspring
2 affected (homozygous) individuals will have affected offspring ONLY (100%)
e.g. cystic fibrosis
disease can skip generations

Question 11

describe the inheritance of autosomal dominant and an example of a disease

Answer 11

heterozygotes affected
males & females equally affected
disease rarely found in homozygous state
every affected individual has 50% chance of having affected offspring
e.g. huntington's disease
affects every generation

Question 12

describe the pattern of x-linked recessive inheritance and an example

Answer 12

hemizygous males and homozygous females affected
disease more common in males
female carriers (heterozygous) have a 50% of having an affected son
affected males can’t pass the trait onto their sons - only from materal line
e.g. haemophilia A
males & females equally affected
affected male will definitely have a heterozygous carrier mother
all affected female have carrier mother and affected father

Question 13

what happens to the dominant allele in co-dominance?

Answer 13

the dominant allele of heterozygote determines the phenotype

Question 14

what happens to the recessive allele in co-dominance?

Answer 14

the non-dominant allele of heterozygote is called recessive

Question 15

example of co-dominance

Answer 15

human ABO blood types
A&B co-dominant
o recessive

Question 16

what is an example of complementation? how many genes produce a phenotype?

Answer 16

albinism - inherited via recessive
2 alleles are both recessive e.g. aa
more than 1 gene can be involved in producing a phenotype

Question 17

genetic variations created by?

Answer 17

1. mutations
2. meiosis:
   independent assortment of chromosomes
   crossing over (recombination)

Question 18

what is linkage in genes?

Answer 18

genes on the same chromosome are ‘linked’

genes on different chromosomes = ‘not-linked’

Question 19

what do linked genes not show?

Answer 19

independent assortment at meiosis (random alignment - as they are on the same chromo(tid)

Question 20

what is recombination frequency in genes?

Answer 20

recombination frequency between 2 linked genes is dependent on the distance between the genes
genes close together are ‘tightly-linked’
genes far apart on the same gene almost behave as unlinked genes