Heredity: Variations and Mutation Flashcards
1
Q
Variations
A
- diff in traits btwn individuals of same species
- indiv traits dependent on interactions btwn genes and environment
- genetic variation is heritable, but variations due to environment is not (e.g fair skin allele)
2
Q
Genetic variation
A
- crossing over (prophase I)
- independent assortment (metaphase I and II)
- random fertilisation (fusion of gametes)
3
Q
Discontinuous variation
A
- controlled by 1 or few genes
- deals with a few clear-cut phenotypes
- no additive effect (no in between) e.g. blood type
- not affected by environmental conditions
- permanent
4
Q
Continuous variation
A
- controlled by additive effect of many genes
- e.g. many genes controlling height, skin colour
- deals with range of phenotypes
- affected by environmental conditions
5
Q
Mutation
A
- a result of error during replication (interphase) of gene/chromosome
- may be inherited by next generation if mutation occur in germline cells (sex cells)
- dominant mutations easily detected, recessive mutations usually hidden
6
Q
Somatic mutation
A
- occur in normal body cells/somatic cells
- cannot be inherited
7
Q
Types of mutation
A
- Chromosome mutation
- Gene mutation
8
Q
Chromosome mutation
A
- change in number/structure of chromosomes
- causes Down’s Syndrome
- extra chromosome, caused by 21st pair
- non-disjunction during anaphase
9
Q
Gene mutation
A
- change in structure of DNA/sequence of nucleotide bases changed
- change in base –> change amino acid –> change structure and function of protein
- substitution, insertion or deletion of nucleotides
- produces variation btwn indiv as results in new alleles of genes
- albinism and sickle-cell anaemia
10
Q
Substitution (Gene mutation)
A
- replace/swap/change bases
11
Q
Insertion/deletion (Gene mutation)
A
- adding or removing base
- affects reading of triplet code
- more dangerous as it results in frameshift
12
Q
Down’s syndrome (Chromosome mutation)
A
- normal humans: 46 chromosomes in body cells
- Down syndrome: 47 chromosomes, extra copy of chromosome 21 (trisomy 21)
- chromosome in mutation in maternal body cell, when split into 2 gametes, 1 has 2 copies of chromosome 21, the other has none
- fuses with male gamete with 1 chromosome 21
- total: 3 chromosome 21 (trisomy 21)
- draw out diagram
13
Q
Albinism (Gene mutation)
A
- caused by mutation in recessive allele
- absence of pigment melanin
- results in reddish-white skin, white hair, pink hair
- get sunburnt easily, sensitive to sunlight
14
Q
Sickle-cell anaemia (Gene mutation)
A
- caused by mutation in gene controlling haemoglobin production
- mutated gene (HbS) is co-dominant to normal gene (HbA)
- both alleles produce their own protein, both expressed
- sickle-shaped red blood cells have low oxygen carrying capacity, tend to clump tgt (blocks blood capillaries)
- fatal, usually die young
15
Q
Sickle-cell anaemia and malaria
A
- heterozygous (carriers) for sickle-cell allele are more resistant
- heterozygous individuals are common in areas where malaria is prevalent e.g. West Africa
