3.1 Genes

Question 1

Define DNA

Answer 1

DNA: genetic blueprint which determines characteristics of an organism

Question 2

DNA structure

Answer 2

DNA - double helix - coiled into chromosomes in histone proteins

Question 3

Define gene

Answer 3

GENE: sequence od DNA which cides for a specific trait (traits may also be influenced by several genes)

Question 4

Define locus

Answer 4

LOCUS: position of a gene on a chromosome (pl loci)

Question 5

Define alleles

Answer 5

ALLELES: alternative forms of a gene that code for different variations of a trait - have similar base sequences

Question 6

Define gene mutation

Answer 6

GENE MUTATION: change in the nucleotide sequence of a section of DNA coding for a specific trait

Question 7

Types of gene mutation effects on proteins

Answer 7

1. Silent: no change in protein
2. Missense: changes protein
3. Nonsense: STOP codon produced instead

Question 8

Real life example of a gene mutation

Answer 8

Sickle cell anaemia

Base subsitution mutation (in gametes) - A mutates into T -> changes am a -> changes haemoglobin shape changes - haemoglobin fibrous in chains not globular and free in RBC -> RBC changes into sickle shape instead of disc -> reduced capacity to carry O₂ + sickle RBC stick to blood vessels - block blood flow

=> person feels constantly tired

Question 9

Benefits of sickle cell anaemia

Answer 9

People containing recessive sickle cell gene are less susceptible to malaria - resist malarial parasite - sickle cell anaemia more common in Africa

Question 10

Define genome

Answer 10

GENOME: the totality of all genetic information in an organelle, cell or organism

Question 11

Different DNA sequences

Answer 11

1. Coding - exons
2. Non - coding: introns, promoters, silencers, STP

Question 12

Significance of Human Genome Project

Answer 12

1. Mapping: number, location, size and sequences of human genes are known
2. Screening: allowed production of gene sequences which allow diagnose diseases
3. Medicine: discovery of new proteins - treatments
4. Ancestry: comparison with other genomes - origin, evolution, migration patterns

Question 13

Comparison of number/similarity of genes

Answer 13

Number or genes varies between species but IS NOT an indicator of biological complexity (human 46 chromosomes, dog 78 chromosomes)

Humans and mouse genomes match 85%, fruit flies 61% - suitable for research

Question 14

Types of gene mutations

Answer 14