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IB HL Biology I > Unit 11 > Flashcards

Unit 11 Flashcards

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1
Q

Heredity

A

the delivery of traits from parent to offspring

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2
Q

Genetics

A

the scientific study of heredity

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3
Q

blending hypothesis

A

inherited traits are determined from the blending together of material from parents

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4
Q

How did Mendel discover the basic principles of heredity?

A

Mendel cross-fertilized pea plants

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5
Q

Cross-fertilization

A

fertilization of one plant from pollen of ANOTHER plant

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6
Q

True Breeding Plant

A

plant that only produces offspring with the same traits when it self-fertilizes

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7
Q

What was Mendel’s argument about his results? (2)

A

1) A unit of heredity can exist in more than 1 form
2) An organism inherits two units of heredity (alleles), one from each parent

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8
Q

Alleles

A

alternate versions of a gene

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9
Q

Dominant Allele

A

allele that is fully expressed in the organism’s appearance

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10
Q

Recessive Allele

A

allele that only influences the organism’s appearance when the dominant allele is not present

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11
Q

Homozygous

A

an organism having a pair of identical alleles for a character

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12
Q

Heterozygous

A

an organism that has two different alleles for a gene

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13
Q

Phenotype

A

an organism’s traits (what you see)

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14
Q

Genotype

A

an organism’s genetic makeup (combination of alleles)

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15
Q

The Law of Segregation

A

Two alleles separate during meiosis so that each gamete contains only one allele for each gene

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16
Q

The Law of Dominance (2)

A
  • if an organism has two alleles, the dominant allele will determine the trait
  • the unexpressed allele is recessive
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17
Q

Punnett Square

A

diagram used to determine the expected ratio of genotypes and phenotypes in the offspring of parents with known genotypes

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18
Q

Testcross

A

a mating between an individual of dominant phenotype and unknown genotype and a homozygous recessive organism

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19
Q

How do you analyze testcross results? (2)

A
  • If all offspring have dominant phenotype, then the parent is homozygous dominant
  • If half offspring have dominant phenotype and half have recessive, then the parent is heterozygous
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20
Q

Dihybrid Cross

A

the crossing of parental varieties differing in two characteristics

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21
Q

What are possible outcomes of a dihybrid cross? (2)

A
  • dependent assortment
  • independent assortment
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22
Q

Dependent Assortment

A

traits are transmitted as a package

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23
Q

Independent Assortment

A

traits are transmitted independently

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24
Q

Law of Independent Assortment

A

the inheritance of one trait has no effect on the inheritance of another

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25
Q

Unlinked Alleles

A

alleles located on different chromosomes

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26
Q

What can unlinked alleles do?

A

move independently during meiosis and get sorted into gametes independently

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27
Q

What is a family pedigree? (2)

A
  • Shows the history of a trait in a family
  • Allows geneticists to analyze how human traits are inherited
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28
Q

How many symbols are used in family pedigrees?

A

2

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29
Q

What are the symbols for male and female on a pedigree?

A
  • circle for female
  • square for male
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30
Q

What indicates that an individual has a disease on a family pedigree?

A

the square or circle is shaded

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31
Q

What does a horizontal line signify on a family pedigree?

A

the parents having children

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32
Q

What does a vertical line signify on a family pedigree?

A

children

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33
Q

What do overhead connections signify?

A

siblings

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34
Q

Wild-type Traits

A

those seen most often in nature (not necessarily dominant!)

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35
Q

How are genetic disorders caused?

A

mutated/changed alleles that alter protein function

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36
Q

What does the loss of normal protein function cause?

A

symptoms of disorders through hypo/hyper activity

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37
Q

Autosomal Disorders

A

mutated genes are on autosomes (not sex chromosomes)

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38
Q

Sex-Linked Disorders

A

disorders-mutated gene is on a sex chromosome

39
Q

Dominant Disorders

A

caused by mutated dominant allele

40
Q

Recessive Disorders (2)

A
  • caused by mutated recessive allele
  • more common
41
Q

How can autosomal recessive disorders appear? (2)

A
  • Homozygous recessive individuals have the disorder
  • Heterozygous individuals are carriers with “normal” phenotype
42
Q

Carrier

A

heterozygous individual who appears normal but carries a recessive disease-causing allele

43
Q

What is an example of an autosomal recessive disorder?

A

cystic fibrosis

44
Q

What is cystic fibrosis?

A

it causes chronic lungs disease

45
Q

What happens with cystic fibrosis as a result of the defective gene? (3)

A
  • thick, sticky mucus that clogs the lungs
  • malabsorption
  • malnutrition
46
Q

How can autosomal dominant disorders appear?(2)

A
  • Heterozygous & homozygous dominant individuals have dominant disorders
  • Only one dominant allele is needed to develop symptoms
47
Q

What is an example of an autosomal dominant disorder?

A

Huntington’s disease

48
Q

What is Huntington’s disease?

A

a neurodegenerative disorder

49
Q

What does the Huntington’s disease protein cause?

A
  • protein aggregates in brain cells
  • death
50
Q

What is a side effect of Huntington’s disease?

A

involuntary movement

51
Q

Genetic Test

A

test that can detect the presence of disease-causing alleles

52
Q

What are genetic tests that can be done? (2)

A
  • amniocentesis
  • chronic villus sampling
53
Q

What are some patterns that cannot be explained by Mendel’s laws? (5)

A

1) multiple alleles
2) codominance
3) polygenic traits
4) pleiotropy
5) environmental factors

54
Q

How many alleles are there for the human ABO gene?

A

3

55
Q

How is the A gene represented?

A

I^A

56
Q

How is the B gene represented?

A

I^B

57
Q

How is the O gene represented?

A

i

58
Q

What are the possible genotypes for A? (2)

A

I^AI^A and I^Ai

59
Q

What are the possible genotypes for B? (2)

A

I^BI^B and I^Bi

60
Q

What is the possible genotype for O

A

ii

61
Q

What is the possible genotype for AB?

A

I^AI^B

62
Q

What blood type is the universal donor?

A

O negative

63
Q

Codominance (2)

A
  • both alleles in the genes pair of a heterozygote are fully expressed
  • no dominant or recessive allele
64
Q

What is an example of codominant alleles?

A

I^A and I^B

65
Q

Polygenic Traits (2)

A
  • exhibit continuous variation
  • many genes control a single trait
66
Q

Continuous Variation

A

phenotypes display a continuous spectrum in the population, not either or

67
Q

What are examples of continuous variation? (2)

A
  • skin color
  • height
68
Q

How is continuous variation created?

A

combining the effects of alleles from multiple genes

69
Q

Pleiotropy

A

when a single gene controls or influences multiple metabolic pathways and has multiple phenotypic effects

70
Q

What disease is an example of pleiotropy?

A

cystic fibrosis

71
Q

Environmental Factors

A

The environment can increase the variation in a trait

72
Q

What are some examples of traits that are controlled by environmental factors? (2)

A
  • human height
  • freckling in humans
73
Q

What are environmental factors that can influence human height? (2)

A
  • diet
  • health
74
Q

What is an environmental factor that can influence freckling?

A

the amount of sunlight and its intensity

75
Q

Biological Sex Determination (4)

A
  • Human somatic cells have 22 pairs of autosomes and 1 pair of sex chromosomes (genes that determine biological sex)
  • Females are XX
  • Males are XY
  • chances of conceiving a male or female child (assigned at birth) are equal
76
Q

Sex-linked traits (3)

A
  • Most sex-linked traits are located on the x chromosome
  • A much smaller number of sex-linked traits are found on the Y-chromosome
  • Sex-linked traits can be recessive or dominant
77
Q

X-linked recessive traits in males (3)

A
  • Males only need 1 recessive allele to have the trait
    -A man with hemophilia is XhY
  • Men are more likely to have recessive X-linked traits because they only have one chance (one X chromosome) to get the healthy allele
78
Q

X-linked recessive traits in females (3)

A
  • Females need 2 recessive alleles to have the trait
    -A woman with hemophilia is XhXh
    -A woman who is a carrier is XHXh
79
Q

What are two examples of X-linked recessive disorders?

A
  • Color blindness
  • Hemophilia
80
Q

What is Hemophilia? (3)

A
  • An x-linked recessive disorder where protein used for blood clotting is not produced
  • Clotting factor proteins are needed to stop bleeding following injury
  • Small injuries can cause excessive bleeding and death
81
Q

What is the inheritance of Hemophilia? (3)

A
  • A man with hemophilia is XhY
  • A woman with hemophilia is XhXh
  • A woman who is a carrier is XHXh
82
Q

What is an X-linked dominant trait? (3)

A
  • Refers to situations where a single dominant allele on the X chromosome can lead to a trait/condition
  • Extremely rare
  • Affected fathers pass the trait to ALL of their daughters in pedigrees
83
Q

What is an example of an X-linked dominant trait? (3)

A
  • X-linked rickets (bone lesions)
  • A man with X-linked rickets is XHY
  • A woman with X-linked rickets is XHXh or XHXH
84
Q

What is independent assortment? (2)

A
  • When the inheritance of one trait has no effect on the inheritance of another
  • Genes on separate chromosomes move through meiosis independently
85
Q

Linked Genes (3)

A
  • are located on the same chromosome
  • move together through meiosis and fertilization
  • are inherited together unless uncoupled by crossing over
86
Q

What is a linkage group?

A

Genes located on the same chromosome

87
Q

Unlinked Genes

A

Located on different chromosomes

88
Q

How does crossing over unlink genes? (2)

A
  • The further apart alleles are on a chromosome, the more likely crossing over will separate them and they will be inherited as though they are not linked
  • Linked alleles located closely on a chromosome are less likely to be separated by crossing over
89
Q

Who was TH Morgan? (2)

A
  • The first to propose the linkage of genes and that characteristics are inherited together
  • When mating fruit flies, his observed offspring ratios that were different from what he predicted assuming independent assortment
90
Q

Key proposals made by TH Morgan (2)

A
  • Alleles for linked traits are on a shared chromosome and don’t independently assort
  • Linked alleles could be uncoupled via crossing over (recombination) to create alternative phenotypic combinations, but these new phenotypes would occur at a much lower frequency
91
Q

What is a parental offspring?

A

Same phenotype as one of the parents

92
Q

What is a recombinant offspring?

A

Phenotypes differ from either parent

93
Q

What is recombinant frequency? (2)

A
  • The percentage of recombinant offspring among the total
  • Calculated by dividing # of recombinants by total offspring and multiplying by 100
94
Q

Why do ‘unlinked’ recombinant phenotypes occur less frequently than the ‘linked’ parental phenotypes?

A

Because crossing over is a random process

IB HL Biology I (10 decks)

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