Genetics

Question 1

Structure of a nucleotide

Answer 1

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

Question 2

Species definition

Answer 2

A group of individuals with shared characteristics

Question 3

Alleles definition

Answer 3

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

Question 4

Chromosomes

Answer 4

DNA tightly wrapped around histones (proteins)

Question 5

Homologous pairs

Answer 5

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

Question 6

Genotype

Answer 6

The inherited genetic make-up of an individual

Question 7

Phenotype

Answer 7

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

Question 8

Monogenic inheritance

Answer 8

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

Question 9

Polygenic Inheritance

Answer 9

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

Question 10

Polygenic inheritance characteristics

Answer 10

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

Question 11

Skin colour - polygenic inheritance

Answer 11

Continuous variation in the trait; affected by environmental factors

Question 12

Effect of genotype on skin colour

Answer 12

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

Question 13

Effect of environmental factors on skin colour

Answer 13

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

Question 14

Dark skin

Answer 14

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

Question 15

Light skin

Answer 15

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

Question 16

Mutagens

Answer 16

Agents that increase the rate at which mutations occur

Question 17

Mutagen examples

Answer 17

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

Question 18

Somatic Mutation

Answer 18

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

Question 19

Germline mutation

Answer 19

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

Question 20

Gene mutation

Answer 20

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

Question 21

Result of a gene mutation

Answer 21

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

Question 22

Point mutation

Answer 22

Change in a single base

Question 23

Albinism

Answer 23

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

Question 24

Duchenne Muscular Dystrophy

Answer 24

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

Question 25

Cystic Fibrosis

Answer 25

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

Question 26

Symptoms of Cystic Fibrosis

Answer 26

Salty tasting skin, persistent coughing, wheezing, digestive problems

Question 27

Chromosomal mutations

Answer 27

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

Question 28

Deletion

Answer 28

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

Question 29

Duplication

Answer 29

A section of a chromosome occurs twice

Question 30

Chromosomal mutations

Answer 30

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

Question 31

Deletion

Answer 31

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

Question 32

Translocation

Answer 32

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

Question 33

Gene Definition

Answer 33

The part of a chromosome that codes for a particular trait

Question 34

Chromosome Definition

Answer 34

Structures carrying hereditary info found in the nucleus of a cell

Question 35

Trisomy

Answer 35

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

Question 36

Non-dysjunction

Answer 36

Failed separation of a chromosome during meiosis - monosomy and trisomy

Question 37

Down Syndrome

Answer 37

extra chromosome 21

Question 38

Trisomy

Answer 38

(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

Question 39

Patus syndrome

Answer 39

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

Question 40

Down Syndrome

Answer 40

extra chromosome 21

Question 41

Klinefelter syndrome

Answer 41

extra x or y chromosome - nondysjunction