DNA

Question 1

what is DNA and where is it found?

Answer 1

found in the nucleus of cells in the body

Question 2

major components of DNA

Answer 2

sugar
phosphates
base

Question 3

4 bases and their pairs

Answer 3

adenine - thymine

cytosine - guanine

Question 4

what is a nucleotide?

Answer 4

is a subunit of the DNA molecule , which consists of one sugar, phosphate and base molecule

Question 5

define a chromosome?

Answer 5

DNA wrapped around proteins called histones

Question 6

what is a gene

Answer 6

a section of DNA that controls a trait

Question 7

what type of cell has a pair of chromosomes?

Answer 7

a somatic cell which is a body cell

Question 8

what type of cell has a single chromosome?

Answer 8

a gamete - which is a sex cell either ova or sperm

Question 9

what is a homologous pair?

Answer 9

a pair of chromosomes containing the pair of genes for a particular trait

Question 10

define alleles

Answer 10

they are the alternative forms of a gene that are available. the pairs of alleles that each person inherits from their parents control and determines the characteristics of the individual

Question 11

how many alleles are in a gene

Answer 11

there are 2 usually one dominant and one recessive (Bb)

Question 12

define a genotype

Answer 12

the genetic makeup of an individual, they are inherited by parents

Question 13

define a phenotype

Answer 13

is the observed expression of the alleles for the characteristic. they are determined by the genotype and the environment

Question 14

what is it called when an individual receives just one pair of alleles for a trait? provide two extremes

Answer 14

monogenic inheritance, traits are discrete. they are either present or absent and there are only to phenotypes

1. blood grouping
2. attached or detached ear lobes

Question 15

what is it called when many pairs of genes control a trait? provide two examples

Answer 15

Polygenic inheritance
there is a continuous variation in the trait 
alleles only have an additive effect
1. skin colour 
2. height

Question 16

what are the three assumptions polygenic inheritance is based on?

Answer 16

1. each gene has two kinds of alleles, contributing and non-contributing
2. there is no dominance
3. the effect of each contributing allele is additive