Genetics Flashcards Preview

Human Biology Unit 4 > Genetics > Flashcards

Flashcards in Genetics Deck (41):
1

Structure of a nucleotide

Sub-unit of DNA - contains a single sugar, phosphate molecule and a nitrogenous base

2

Species definition

A group of individuals with shared characteristics

3

Alleles definition

Alternative forms of a gene; inherited from their parent and control/determine characteristics

4

Chromosomes

DNA tightly wrapped around histones (proteins)

5

Homologous pairs

A pair of genes coding for a particular trait (dominant, recessive, co-dominant)

6

Genotype

The inherited genetic make-up of an individual

7

Phenotype

The observed expression of the alleles for a characteristic - determined by genotype and the environment

8

Monogenic inheritance

A single pair of alleles is inherited for a particular trait; eg. blood type - these traits are discrete (either there or not) and have only two phenotypes

9

Polygenic Inheritance

Controlled by multiple pairs of genes, thus continuous variation in trait - Alleles have an additive effect (skin colour, weight, height)

10

Polygenic inheritance characteristics

Each gene has 2 forms of alleles - contributing and non-contributing
No dominance
Additive effect

11

Skin colour - polygenic inheritance

Continuous variation in the trait; affected by environmental factors

12

Effect of genotype on skin colour

Varying amounts of the enzyme tyrosinase (stimulated by UV rays to produce melanin)

13

Effect of environmental factors on skin colour

UV light stimulates the production of tyrosine (aa forming melanin- protein)

14

Dark skin

High levels of tyrosinase; increased ability to convert tyrosine to melanin
More even distribution of melanin - more tanned, less susceptible to sun burn

15

Light skin

Low levels of tyrosinase; decreased ability to convert tryosine to melanin
Less even distribution of melanin (freckles) - less tanned, more susceptible to sun burn

16

Mutagens

Agents that increase the rate at which mutations occur

17

Mutagen examples

UV light, X-rays, radiation, chemicals (sulphur dioxide, antibiotics)

18

Somatic Mutation

Occurs in a body cell - isn't past through to next generation

19

Germline mutation

Occurs in the gametes - doesn't affect individual, does affect offspring

20

Gene mutation

Change in a single gene - occurs in the replication of a DNA molecule before cell division

21

Result of a gene mutation

May code for a new amino acid thus a new protein, protein may be missing, no change

22

Point mutation

Change in a single base

23

Albinism

Point mutation in TYR gene - results in missing protein responsible for pigment

24

Duchenne Muscular Dystrophy

Point mutation results in missing protein dystrophin - leads to wasting of leg muscles, later other muscles; experienced at 3-5 years, resulting in death by 25 due to failure of respiratory muscles

25

Cystic Fibrosis

Point mutation at CFTR gene, results in different amino acids in CFTR protein; regulates development of chloride channels in cell membrane - absence means chloride ions, water can't be transported through cells

26

Symptoms of Cystic Fibrosis

Salty tasting skin, persistent coughing, wheezing, digestive problems

27

Chromosomal mutations

Changes in whole/part of a chromosome - many genes can be affected, many symptoms; deletion, duplication, inversion

28

Deletion

Part of the chromosome is lost/removed - results in a shorter chromosome

29

Duplication

A section of a chromosome occurs twice

30

Chromosomal mutations

Changes in whole/part of a chromosome - many genes can be affected, many symptoms; deletion, duplication, inversion

31

Deletion

Part of the chromosome is lost/removed - results in a shorter chromosome - can occur as a gene or a chromosomal mutation

32

Translocation

Part of the chromosome breaks off and reattaches to the wrong chromosome

33

Gene Definition

The part of a chromosome that codes for a particular trait

34

Chromosome Definition

Structures carrying hereditary info found in the nucleus of a cell

35

Trisomy

(Non-dysjunction) - failure of one or more chromatids to separate in the second division of mitosis
down syndrome, patus syndrome, klinefelter syndrome

36

Non-dysjunction

Failed separation of a chromosome during meiosis - monosomy and trisomy

37

Down Syndrome

extra chromosome 21

38

Trisomy

(Non-dysjunction) Down syndrome - extra chromosome 21
Patus syndrome - extra chromosome 13; mental retardation, small head, extra finger, cleft palate, malformation of the eyes and ears
Klin

39

Patus syndrome

extra chromosome 13; mental retardation, small head, extra finger, cleft palate, malformation of the eyes and ears

40

Down Syndrome

extra chromosome 21

41

Klinefelter syndrome

extra x or y chromosome - nondysjunction