Bioloigy Variation GSCE Flash Cards

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82 Terms

1
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Sex chromosomes
The two chromosomes that determine biological sex: XX for females, XY for males.
2
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Y chromosome function
It carries a gene that overrides female development and triggers male reproductive system development.
3
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Male development timing
Occurs about 6–8 weeks after fertilisation.
4
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Genes on X chromosome
Over 100 genes.
5
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Gene
Section of DNA that codes for a protein.
6
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Allele
Different versions of the same gene.
7
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Homozygous
Having two identical alleles for a gene.
8
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Heterozygous
Having two different alleles for a gene.
9
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Dominant allele
Always expressed in the phenotype if present.
10
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Recessive allele
Only expressed if two copies are present.
11
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Genotype
The combination of alleles for a gene.
12
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Phenotype
The observable traits resulting from genotype and environment.
13
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Gregor Mendel
An Austrian monk who studied inheritance in pea plants.
14
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Mendel’s discovery
Characteristics are inherited as distinct units—genes—not blended.
15
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Probability of male or female baby
50% male, 50% female.
16
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Genetic cross
A diagram showing how alleles combine during fertilisation.
17
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Punnett square
Used to predict the probability of offspring traits.
18
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Dominant alleles
Represented by capital letters.
19
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Recessive alleles
Represented by lowercase letters.
20
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Mendel’s pea plant results
Red is dominant; white is recessive. Crossing red × white gives all red flowers.
21
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RR genotype
Homozygous dominant → red flowers.
22
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Rr genotype
Heterozygous → red flowers.
23
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rr genotype
Homozygous recessive → white flowers.
24
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Cross: GG × gg
Offspring are 100% Gg (green pods, heterozygous).
25
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Cross: Gg × Gg
75% green pods, 25% yellow pods.
26
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Brown eyes (B) vs blue eyes (b)
B is dominant to b; BB × bb = 100% Bb (brown eyes).
27
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Cross: Bb × bb
50% brown eyes (Bb), 50% blue eyes (bb).
28
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Probability in genetics
The likelihood a genotype or phenotype will occur.
29
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Cystic fibrosis
A disorder affecting cell membranes, lungs, and pancreas, causing excess mucus.
30
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Cystic fibrosis inheritance
Recessive condition.
31
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Cystic fibrosis genotypes
CC = healthy, Cc = carrier, cc = has cystic fibrosis.
32
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Two carrier parents
25% healthy, 50% carrier, 25% sufferer.
33
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Huntington’s disease
A dominant disorder affecting the nervous system; symptoms appear age 30–50.
34
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Huntington’s inheritance
Only one faulty dominant allele needed to have the disorder.
35
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Huntington’s genotypes
Hh = has disease, hh = healthy.
36
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Polydactyly
A dominant genetic disorder causing extra fingers or toes.
37
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Homozygous definition
Two identical alleles for a gene.
38
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Heterozygous definition
Two different alleles for a gene.
39
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Dominant definition
Expressed if present in the genotype.
40
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Recessive definition
Expressed only if two copies are present.
41
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42
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Sex chromosomes
The two chromosomes that determine biological sex: XX for females, XY for males.
43
New cards
Y chromosome function
It carries a gene that overrides female development and triggers male reproductive system development.
44
New cards
Male development timing
Occurs about 6–8 weeks after fertilisation.
45
New cards
Genes on X chromosome
Over 100 genes.
46
New cards
Gene
Section of DNA that codes for a protein.
47
New cards
Allele
Different versions of the same gene.
48
New cards
Homozygous
Having two identical alleles for a gene.
49
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Heterozygous
Having two different alleles for a gene.
50
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Dominant allele
Always expressed in the phenotype if present.
51
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Recessive allele
Only expressed if two copies are present.
52
New cards
Genotype
The combination of alleles for a gene.
53
New cards
Phenotype
The observable traits resulting from genotype and environment.
54
New cards
Gregor Mendel
An Austrian monk who studied inheritance in pea plants.
55
New cards
Mendel’s discovery
Characteristics are inherited as distinct units—genes—not blended.
56
New cards
Probability of male or female baby
50% male, 50% female.
57
New cards
Genetic cross
A diagram showing how alleles combine during fertilisation.
58
New cards
Punnett square
Used to predict the probability of offspring traits.
59
New cards
Dominant alleles
Represented by capital letters.
60
New cards
Recessive alleles
Represented by lowercase letters.
61
New cards
Mendel’s pea plant results
Red is dominant; white is recessive. Crossing red × white gives all red flowers.
62
New cards
RR genotype
Homozygous dominant → red flowers.
63
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Rr genotype
Heterozygous → red flowers.
64
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rr genotype
Homozygous recessive → white flowers.
65
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Cross: GG × gg
Offspring are 100% Gg (green pods, heterozygous).
66
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Cross: Gg × Gg
75% green pods, 25% yellow pods.
67
New cards
Brown eyes (B) vs blue eyes (b)
B is dominant to b; BB × bb = 100% Bb (brown eyes).
68
New cards
Cross: Bb × bb
50% brown eyes (Bb), 50% blue eyes (bb).
69
New cards
Probability in genetics
The likelihood a genotype or phenotype will occur.
70
New cards
Cystic fibrosis
A disorder affecting cell membranes, lungs, and pancreas, causing excess mucus.
71
New cards
Cystic fibrosis inheritance
Recessive condition.
72
New cards
Cystic fibrosis genotypes
CC = healthy, Cc = carrier, cc = has cystic fibrosis.
73
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Two carrier parents
25% healthy, 50% carrier, 25% sufferer.
74
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Huntington’s disease
A dominant disorder affecting the nervous system; symptoms appear age 30–50.
75
New cards
Huntington’s inheritance
Only one faulty dominant allele needed to have the disorder.
76
New cards
Huntington’s genotypes
Hh = has disease, hh = healthy.
77
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Polydactyly
A dominant genetic disorder causing extra fingers or toes.
78
New cards
Homozygous definition
Two identical alleles for a gene.
79
New cards
Heterozygous definition
Two different alleles for a gene.
80
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Dominant definition
Expressed if present in the genotype.
81
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Recessive definition
Expressed only if two copies are present.
82
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