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SAT II Biology > Chapter 6 > Flashcards

Chapter 6 Flashcards

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1
Q

Father of modern genetics

A

Gregor Mendel (austrian monk)

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2
Q

What did gregor mendel do?

A
  1. Bred garden peas to study patterns of heredity

2. Statistically analyzed hundreds of plants across many generations

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3
Q

What did gregor mendel do?

A
  1. Bred garden peas to study patterns of heredity

2. Statistically analyzed hundreds of plants across many generations

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4
Q

Mendel’s work produced which laws:

A

Law of dominance, law of segregation, and law of independent assortment

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5
Q

Probability

A

likelihood a particular event will occur but it can’t predict whether event will actually occur

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6
Q

If sample is large enough

A

can predict an average outcome

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7
Q

Law of Dominance

A

This law states that when two organisms, homozygous (pure) for 2 opposing traits are crossed, the offspring will be hybrid (carry 2 diff alleles) but will exhibit only the dominant trait

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8
Q

Hidden trait is the

A

recessive one

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9
Q

Law of Segregation

A

State that during the formation of gametes, the 2 traits carried by each parent separate

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10
Q

Monohybrid cross

A

a cross between 2 organisms that are each hybrid for a single trait

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11
Q

Monohybrid cross percentages

A

The genotype (types of genes) ratio is 25% homozygous dominant (TT) to 50% heterozygous (Tt) to 25% homozygous recessive (tt) or 1 : 2: 1.

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12
Q

Backcross or Testcross

A

a way to determine whether an individual plant or animal showing the dominant trait is homozygous dominant (BB) or heterozygous (Bb)

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13
Q

Backcross/Testcross Step 1

A
  1. To determine genotype, an individual of the unknown genotype (B_) is crossed with a homozygous recessive individual (bb)
    The genotype B_ means that oen allele is dominant (B) but the other is uncertain, B/B or B/b
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14
Q

Backcross/Testcross Step 2

A
  1. If the individual being tested is homozygous dominant (BB) → all offspring of the test cross will show the dominant trait and have a hybrid (Bb) genotype
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15
Q

Backcross/Testcross Step 4

A
  1. If the individual being test is actually hybrid (Bb), we can expect that ½ of the offspring, or at least 1 individual, will show the recessive trait
    Therefore, if any offspring show the recessive trait, the parent of unknown genotype must be hybrid
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16
Q

Law of Independent Assortment

A

This law states that during gamete formation, the genes for one trait (such as height, T or t) are not inherited along with the genes for another trait (such as seed color, Y or y )

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17
Q

What does the law of independent assortment apply to?

A

This applies when a cross is carried out between 2 individuals that are hybrid for 2 traits on separate chromosomes

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18
Q

What factor determines how alleles are inherited?

A

how the homologous pair ( in this case TY and ty) happen to line up in metaphase of meiosis I, which is a random event

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19
Q

Crossing Tt Yy x Tt Yy is called

A

a dihybrid cross because it is a cross between individuals that are hybrid for 2 different traits

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20
Q

A dihybrid cross can produce

A

4 diff types of gametes TY, Ty, tY, and ty

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21
Q

Incomplete Dominance

A

characterized by blending

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22
Q

Examples of incomplete dominance

A
  1. A long watermelon (LL) crossed with a round watermelon (RR) produces all oval watermelons (RL)
  2. A black animal (BB) crossed with a white (WW) animal produces all gray (BW) animals
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23
Q

(In incomplete dominance) Since neither trait is dominant,

A

the convention for writing the genes uses different capital letters

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24
Q

Codominance

A

both traits show

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25
Q

Example of codominance

A

the MN blood group in humans ( not related to ABO blood group)

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26
Q

3 Diff blood groups: M, N, MN

A

these groups are based on 2 distinct molecules located on the surface of the red blood cells.

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27
Q

A person can be

A

1) homozygous for 1 type of molecule ((MM), homozygous for the other (NN), or be hybrid and have both molecules (MN) on the surface of their red blood cells.

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28
Q

MN gentoype is not intermediate between M and N,

A

both M and N are fully expressed on the surface of red blood cells

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29
Q

Multiple Alleles

A

Most genes in a population exist in only 2 allelic forms (ex. Pea plants can either be tall (T) or dwarf (t))

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30
Q

Example of Multiple Allele

A

in humans there are 4 diff blood groups depending on the presence of specific molecules on the surface of RBCs: A, B, AB, AND O

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31
Q

Four diff blood types determined by

A

3 alleles A, B, AND O.

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32
Q

A and B are codominant and are often written as

A

I ^A and I^ B ( i stands for immunoglobulin).

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33
Q

When both alleles are present (A/B), they are both expressed

A

and the person has AB blood type

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34
Q

O is a

A

recessive trait often written as i

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35
Q

Blood Type: A

Genotype: homozygous A:

A

AA

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35
Q

Blood Type: A

Genotype: hybrid A:

A

Ai

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36
Q

Blood Type: B

Genotype: homozygous B:

A

BB

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37
Q

Blood Type: B

Genotype: hybrid B:

A

Bi

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38
Q

Blood Type: AB

Genotype: heterozygous:

A

AB

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39
Q

Blood Type: O

Genotype: homozygous O:

A

ii

40
Q

A person can have any one of the

A

6 blood genotypes

41
Q

Polygenic Inheritance

A

Height and other similar features are controlled by not just one gene but multiple genes that each make a small contribution to the overall outcome

42
Q

Many characteristics such as skin color, hair color, and height result from a

A

blending of several separate genes that vary along a continuum , they are controlled by several genes

43
Q

Sex-Linked Genes

A

Traits carried on the X chromosome are called sex-linked

44
Q

Females inherit

A

two copies of sex-linked genes (XX)

45
Q

If a sex-linked trait is due to a recessive mutation, a female will

A

express the phenotype only if she carries 2 mutated genes (X-, X-)

46
Q

If she carries only one mutated X-linked gene

A

she will be a carrier (X-X)

47
Q

Males (XY) only inherit

A

one X-linked gene

48
Q

If the male inherits a mutated X-linked gene (X-Y),

A

he will express the gene

49
Q

There are dominant sex-linked traits

A

but recessive ones are much more common

50
Q

Who suffers with sex-linked traits more?

A

females more than males

51
Q

Common examples of recessive sex-linked traits

A

color blindness and hemophilia

52
Q

Who are the carriers?

A

All daughters of affected fathers

53
Q

Sons cant inherit a sex-linked trait from the father because

A

the son inherits the Y chromosome from the father

54
Q

What is the chance a son inherits a sex-linked trait from a carrier mother?

A

50%

55
Q

What is the carrier state for X-linked traits in males?

A

there is no carrier state

if a male has the gene, he will express it

56
Q

It is uncommon for a female to express a sex-linked condition because

A

in order to be affected, she must have inherited a mutant gene from both parents

57
Q

In sex-linked inheritance, the father

A

passes the trait to his daughters only

58
Q

What can alter the expression of genes?

A

the environment

59
Q

In fruit flies, the expression of the mutation for vestigial wings (short, shriveled wings)

A

can be altered by temperature

60
Q

When raised in a hot environment, fruit flies that are

A

homozygous recessive for vestigial wings can grows almost as long as normal wings

61
Q

For humans, the development of intelligence is the result of

A

an interaction of genetic predispositions and the influence of the environment

62
Q

Inheritance can be influenced by the

A

sex of the individual carrying the traits.

63
Q

Pattern of baldness in males is not

A

sex-linked but rather sex-influenced

64
Q

Males and females express the gene for pattern baldness

A

differently

65
Q

Karyotype

A

Type of lab procedure that analyzes the size, shape, and number of chromosomes

66
Q

When do specialists prepare and photograph chromosomes for karyotypes?

A

during metaphase of mitosis when they are fully condensed

67
Q

In human chromosomes

A

44 (22 pairs) autosomes and 2 sex chromosomes

68
Q

Pedigree

A

A family tree that indicates the phenotype of 1 trait being studied for every member of a family

69
Q

Why do geneticists use pedigrees?

A

to determine how a specific trait is inherited

70
Q

Pedigrees
Female:
Male:

A

circle

square

71
Q

Carrier state in pedigrees

A

Carrier state is not always shown

-if it is, it is sometimes represented by a half-shaded in shape

72
Q

A shape completely shaded in if a

A

person exhibits the trait

73
Q

Mutations

A

Any abnormality in the genome → can occur in somatic (body) cells and be responsible for the spontaneous development of cancer

74
Q

Mutations can also occur

A

during gametogenesis in germ cells and affect future offspring

75
Q

When and where mutations occur is

A

random

76
Q

2 Types of mutations

A

Gene and Chromosome

77
Q

Gene Mutations

A

caused by change in DNA sequence.

78
Q

Chromosome mutations

A

can be observed under a light microscope.
A chromosome may sustain a deletion or an addition or a cell may have an entirely extra chromosome, which results from nondisjunction

79
Q

Nondisjunction

A

An error that sometimes happens during meiosis in which homologous chromosomes fail to separate as they should

80
Q

When nondisjunction occurs

A

1 gamete receives 2 homologues, while the other gamete recipes none → remaining chromosomes may be unaffected and normal

81
Q

If either of these abnormal gametes unties with a normal gamete during fertilization

A

the resulting zygote will have an abnormal number of chromosomes

82
Q

Any abnormal chromosome condition is known as

A

aneuploidy

83
Q

trisomy

A

If the chromosome is present in triplicate

84
Q

Down syndrome

A

3 #21 chromosomes →trisomy-21

85
Q

Triploid (3n)

A

An organism in which the cells have an extra set of chromosomes

86
Q

Examples of triploid

A

The cells of endosperm or cotyledon of a seed are triploid

87
Q

Polyploid

A

An organism with more than 3 sets of chromosomes

88
Q

Why do scientists breed plants to be polyploid?

A

because they will produce abnormally large flowers and fruit

89
Q

Human-Inherited Disorders

A

Can either be caused by a gene or chromosome mutation

89
Q

Human-Inherited Disorders

A

Can either be caused by a gene or chromosome mutation

90
Q

Gene mutations are not

Chromosomal mutations can be assessed by

A

visible under a microscope

doing karyotypes

91
Q

Karyotypes are usually carried out on

A

cells from a developing fetus to scan for chromosomal abnormalities such as trisomy-21

92
Q

Chromosomal aberrations (abnormalities) include:

A

deletion, inversion, translocation, polyploidy, nondisjunction

93
Q

Deletion

A

fragment lacking a centromere is lost during cell division

94
Q

Inversion

A

a chromosomal fragment reattaches to its original chromosome but in reverse orientation

95
Q

Translocation

A

fragment of a chromosome becomes attached to a nonhomologous chromosome

96
Q

Polyploidy

A

cell or organisms has extra sets of chromosomes

97
Q

Nondisjunction

A

homologous chromosomes fail to separate during meiosis

SAT II Biology (15 decks)

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