Genetics and Inheritance

Question 1

Gene

Answer 1

a unit of inheritance, a length of DNA that codes for a particular polypeptide or protein

Question 2

Allele

Answer 2

1 or 2 or more alternative nucleotide sequences at a single gene locus; variant forms of genes

Question 3

Locus

Answer 3

position on the chromosomes where a gene occurs; alleles of the same gene occupy the same locus

Question 4

Dominant allele

Answer 4

an allele with a phenotype that is expressed even when present with an allele that is recessive to it e.g. H

Question 5

Recessive allele

Answer 5

an allele with a phenotype that is not expressed when an allele that is dominant to it is present e.g. h

Question 6

Homozygous

Answer 6

a genotype in which the 2 alleles of a gene are the same e.g. HH, hh

Question 7

Heterozygous

Answer 7

a genotype in which the 2 alleles of a gene are different e.g. Hh

Question 8

Genotype

Answer 8

the alleles that an organism carries (present in every cell)

Question 9

Phenotype

Answer 9

the appearance of the organism; the way in which the genotype of the organism is expressed

Question 10

HH

Answer 10

Homozygous dominant

Question 11

Hh

Answer 11

Heterozygous

Question 12

hh

Answer 12

Homozygous recessive

Question 13

Explain why observed ratios often differ from expected ratios, especially when there are small numbers of progeny.

Answer 13

It’s a probability

The smaller the sample size, the lower the probability of the observed ratio being similar to the expected ratio

Question 14

how genes are inherited from one generation to the next generation via the gametes.

Answer 14

• In sexual reproduction, haploid gametes are formed by meiosis
• At fertilization, male and female gametes fuse to form a zygote, a diploid cell, which has 2 sets of chromosomes (homologous pairs), one from each parent
• There are 2 alleles of each gene present in the new individual