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Flashcards in Genetics Unit Test PPT. Deck (111):
1

study of genetics

- Study of how traits are passed from parent to offspring
- heredity
- inheritance

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Gregor Mendel

- Father of Genetics
- Mathematician
- Experimented with pea plant traits to follow inheritance

3

What structures does the perfect flower have?

male and female structures

4

anther

- male structure
- produces pollen containing sperm

5

ovary

- female structure
- Produces ovules containing eggs

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Mendel's Experiment

1. Grew pure plants (P generation) that had 2 of the same alleles.
2. Cross pollinated plants with contrasting traits to create F1 generation
3. Cross two F1 tall plants to get the F2

7

Law of Segregation

- During meiosis I homologous chromosomes separate.
- Offspring receives one gene for a trait from each parent.

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1N

haploid

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2N

diploid

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punnett square

- Used to predict the chances of offspring genotypes.
- Outcome is based on large number of offspring.

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Mendel's Generations

- P generation
- F1 generation (Hybrid 4:0)
- F2 generation (3:1 ratio)

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Parental (P) generation

pure for a trait

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F2 generation

Offspring of F1

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Law of Independent Assortment

Inheritance of one trait has no effect on the inheritance of another trait when genes are on separate chromosomes

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What are traits determined by?

the genes on the chromosomes

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gene

a segment of DNA that determines a trait

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What do chromosomes come in?

homologous pairs

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What do genes come in?

pairs

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homologous pairs

matching genes – one from female parent and one from male parent

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Example of Homologous Pairs:
Humans have 46 chromosomes or 23 pairs.

One set from dad – 23 in sperm
One set from mom – 23 in egg

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alleles

different genes (possibilities) for the same trait –
ex: blue eyes or brown eyes

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dominant allele

prevents the other allele from being expresses

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recessive allele

is NOT expressed even though it is present in the DNA

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symbol for dominant allele

upper case letter

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symbol for recessive gene

lower case letter

26

How can a recessive trait be expressed?

Must have 2 recessive alleles for a recessive trait to be expressed

27

Always use the ____ letter for the same alleles.

same

28

Straight thumb is ______ to hitchhiker thumb

dominant

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homozygous or purebred

Both genes of a pair are the same

ex.
TT – homozygous dominant
tt – homozygous recessive

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heterozygous or hybrid

One dominant and one recessive gene

ex.
Tt – heterozygous

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genotype

Combination of genes an organism has (actual gene makeup)

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What is an example of a genotype?

Ex: TT, Tt, tt

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phenotype

Physical appearance resulting from gene make-up

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What is an example of a phenotype?

Ex: hitchhiker’s thumb or straight thumb

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What does probability mean?

The chance of an event occurring

36

In order to get close to the predicted, what do you have to many of?

NEED MANY TRIALS

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What is the punnett square based on?

many offspring (trials)

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What is the punnett square used for?

Used to predict the possible gene makeup of offspring

39

karyotype

picture of an individual’s chromosomes

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amniocentesis

amniotic fluid surrounding the embryo is removed for analysis

41

Dwarfism

variety of skeletal abnormalities

42

Huntington's Disease

gradual deterioration of brain tissue, shows up in middle age and is fatal

43

What are dominant gene mutations?

- dwarfism
- huntington's disease

44

Phenylketonuria (PKU)

- an amino acid common in milk cannot be broken down and as it builds up it causes mental retardation
- newborns are tested for this

45

Cystic fibrosis

mucous builds up in the lungs

46

Tay-Sachs Disease

- deterioration of the nervous system
- early death

47

What do mutated genes produce?

produce enzymes that are less effective than normal at breaking down fatty cell products known as gangliosides

48

What happens as result of what the mutated genes produced?

gangliosides build up in the lysosomes and overload cells. Their buildup ultimately causes damage to nerve cells

49

What are recessive gene mutations?

- sickle cell anemia
- Cystic fibrosis
- Tay-Sachs Disease
- Phenylketonuria

50

Sickle cell anemia

- red blood cells are sickle shaped instead of round and cannot carry enough oxygen to the body tissues
- heterozygous condition protects people from malaria

51

Gene or Point Mutation

- most common and least drastic
- only one gene is altered

52

What does the inside of punnett squares represent?

possible offspring (2N)

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What does the outside of the punnett square represent?

Male gametes - N (One gene in sperm) or
Female gametes – N (One gene in egg)

54

What is the order to write a genotypic ratio?

homozygous dominant : heterozygous : homozygous recessive

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What is the order to write a phenotypic ratio?

dominant : recessive

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People have ___ chromosomes or ___ pairs.

- 46
- 23

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homologous

look alike

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autosomes

determine body traits

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22 pairs are _________.

homologous

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What are the 22 homologous pairs called?

autosomes

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1 pair is a ____ chromosome

sex

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sex chromosomes

determines sex (male or female)

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Female

- sex chromosomes are homologous (look alike)
- label XX

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Male

- sex chromosomes are different
- label XY

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What is the probability of a couple having a boy? Or a girl?

50/50 chance

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incomplete dominance

When one allele is NOT completely dominant over another they produce a blended phenotype

67

What is an example of incomplete dominance?

In carnations the color red (R) is incompletely dominant over white (W). The hybrid color is pink.

68

codominance

When both alleles are expressed individually

69

What is an example of complete dominance?

- In certain chickens black feathers are codominant with white feathers.
- Heterozygous chickens have black and white speckled feathers.

70

ROAN Cow

Red allele: R
White allele: W
Roan: RW

71

Blood Type Alleles

Alleles for a protein on the Red Blood Cell

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I^A

Alpha protein

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I^B

Beta protein

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i^o or i

neither

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Possible Blood genotypes

- Type A
- Type B
- Type AB
- Type O

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SRY

Sex determining Region of the Y

77

Sex-linked traits

Genes for these traits are located only on the X chromosome (NOT on the Y chromosome)

78

Why are x-linked alleles expressed in males whether dominant or recessive?

males have only one X chromosome

79

What are examples of recessive sex-linked disorders?

- colorblindness
- hemophilia

80

colorblindness

inability to distinguish between certain colors

81

What is the most common type of color blindness?

red-green color blindness, where red and green are seen as the same color

82

hemophilia

blood won’t clot

83

Barr body

- In females one X chromosome is inactivated in each cell.
- Some cells have one X turned off and some cells have the other X turned off.

84

Calico Cat color expression

X^B X^O

85

pedigree

Diagram of a trait passed through generations

86

circles =

females

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squares =

males

88

horizontal lines =

marriage

89

Vertical line and brackets =

connect parent to offspring

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A shaded circle or square =

person has the trait

91

A circle or square NOT shaded =

an individual who does NOT have the trait

92

Partial shade =

carrier/ heterozygous for the trait

93

multiple alleles

3 or more alleles of the same gene that code for a single trait

94

In humans, blood types are determined by how many alleles?

3 alleles - A, B, and O

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How many alleles from blood types do humans actually inherit?

inherit 2 alleles

96

Dominant Blood Type Alleles

A and B (codominance)

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Recessive Blood Type Alleles

O

98

What are possible blood types?

A = AA or AO
B = BB or BO
AB = AB
O = OO

99

mutation

sudden genetic change (change in base pair sequence of DNA)

100

How can mutations be?

- harmful
- beneficial
- neutral

101

Harmful mutations

organism less able to survive: genetic disorders, cancer, death

102

Beneficial mutations

allows organism to better survive: provides genetic variation

103

Neutral mutations

neither harmful nor helpful to organism

104

What are the two ways a mutation can occur?

chromosomal mutation or gene/point mutation

105

chromosomal mutation

- less common than a gene mutation
- more drastic – affects entire chromosome, so affects many genes rather than just one
- caused by failure of the homologous chromosomes to separate normally during meiosis
- chromosome pairs no longer look the same – too few or too many genes, different shape

106

What are examples of chromosomal mutations?

- Down syndrome
- Turner's syndrome
- Klinefelter’s syndrome

107

Down syndrome

(Trisomy 21) 47 chromosomes, extra chromosome at pair #21

108

Turner’s syndrome

- only 45 chromosomes, missing a sex chromosome (X)
- Girls affected – short, slow growth, heart problems

109

Klinefelter’s syndrome

- 47 chromosomes, extra X chromosomes (XXY)
- Boys affected – low testosterone levels, underdeveloped muscles, sparse facial hair

110

What can happen if there is an extra set of chromosomes in animals?

fatal in animals

111

What can happen if there is an extra set of chromosomes in plants?

it makes them larger and hardier