Topic 3.1: Genes

Question 1

Gene

Answer 1

A heritable factor that consists of a sequence of DNA and influences a specific trait

Question 2

Locus

Answer 2

The position of a gene on a particular chromosome

Question 3

Alleles

Answer 3

Alternative forms of a gene that code for the different variations of a specific trait

Question 4

How do alleles of the same gene differ from each other?

Answer 4

By one or a few bases

Question 5

How may new alleles be formed?

Answer 5

As a result of gene mutations

Question 6

Gene mutation

Answer 6

A change in the nucleotide sequence of a section of DNA coding for a specific trait

Question 7

Types of consequences of a gene mutation

Answer 7

a) Beneficial (Missense)
b) Detrimental (Nonsense)
c) Neutral (Silent)

Question 8

Beneficial mutations

Answer 8

Create new variations of a trait

Question 9

Detrimental mutations

Answer 9

Truncate the gene sequence to abrogate the normal function of a trait

Question 10

Neutral mutations

Answer 10

Have no effect on the functioning of the specific feature

Question 11

Cause of Sickle Cell Anemia

Answer 11

a) Base substitution: GAG → GUG (6th codon: hemoglobin beta)

b) Amino acid change: Glutamic acid → Valine (Glu → Val)

Question 12

Consequences of Sickle Cell Anemia

Answer 12

a) Alters hemoglobin structure (forms insoluble strands)
b) Cannot transport oxygen effectively (causing fatigue)
c) Red blood cells adopt a sickle shape (may form clots)
d) Sickle cells are destroyed at a higher rate (causes anemia)

Question 13

Heterozygous Advantage of Sickle Cell Anemia

Answer 13

Sickle cell anemia is a codominant trait and heterozygous individuals demonstrate an increased resistance to malaria

Question 14

Genome

Answer 14

The totality of the genetic information in an organism (Genes / Non-coding sequences)

Question 15

Human Genome

Answer 15

46 chromosomes
~3 billion base pairs
~21,000 genes

Question 16

Human Genome Project

Answer 16

International cooperative venture established to sequence the human genome in 2003

Question 17

Outcomes of the HGP

Answer 17

a) Mapping – The number, location, size and sequence of human genes
b) Screening – Production of gene probes to detect sufferers and carriers of genetic diseases

Question 18

Genetic comparison

Answer 18

There is no clear correlation between genetic complexity and chromosome numbers, genome size or the number of genes

Question 19

Point mutations

Answer 19

Changes to one base in the DNA code

Question 20

Types of point mutations

Answer 20

a) Substitution (ATG - ACG)
b) Insertion (ATG - ATCG)
c) Deletion (ATG - AG)
d) Inversion (ATG - AGT)

Question 21

Effects of Point Mutations

Answer 21

a) Silent (No alterations)
b) Missense (Alters a single amino acid)
c) Nonsense (Creates a STOP codon)
d) Frameshift (Alters the amino acid sequence)