Topic 3.1: Genes Flashcards Preview

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Flashcards in Topic 3.1: Genes Deck (21)
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1

Gene

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

2

Locus

The position of a gene on a particular chromosome

3

Alleles

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

4

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

By one or a few bases

5

How may new alleles be formed?

As a result of gene mutations

6

Gene mutation

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

7

Types of consequences of a gene mutation

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

8

Beneficial mutations

Create new variations of a trait

9

Detrimental mutations

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

10

Neutral mutations

Have no effect on the functioning of the specific feature

11

Cause of Sickle Cell Anemia

a) Base substitution: GAG → GUG (6th codon: hemoglobin beta)
b) Amino acid change: Glutamic acid → Valine (Glu → Val)

12

Consequences of Sickle Cell Anemia

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)

13

Heterozygous Advantage of Sickle Cell Anemia

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

14

Genome

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

15

Human Genome

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

16

Human Genome Project

International cooperative venture established to sequence the human genome in 2003

17

Outcomes of the HGP

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

18

Genetic comparison

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

19

Point mutations

Changes to one base in the DNA code

20

Types of point mutations

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

21

Effects of Point Mutations

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