Mendelian Genetics Flashcards

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1
Q

Gregor Mendel

A

“The father of Modern Genetics”

–> Started out as a monk growing peas

–> In 1865, he published a paper that reported on his pea plant experiments that suggested a model for how traits are inherited

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2
Q

Mendel was the first to…

A

Deduce clear laws that explained the process and patterns of inheritance (through experimental observations and mathematics)

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3
Q

2 major hypotheses existed for inheritance of traits:

A

1) The “Blending” Hypothesis
2) Inheritance of Acquired Characters Hypothesis

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4
Q

Blending Hypothesis

A

Genetic material contributed by BOTH parents MIX together (blend)

Ex: Black + White Sheep = Grey Sheep

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5
Q

Inheritance of Acquired Characters Hypothesis

A

Experience Dependent Inheritance

–> An organism passes on traits that the parent acquired through use/disuse in its lifetime

EX: The passing down of long necks in giraffes due to parents stretching to reach high hanging fruit

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6
Q

Benefits of the pea plant model (5)

A

1) Easy + Inexpensive to cultivate
2) Reproduce Quickly (short generation time)
3) Lots of variety in pea plants that are easily distinguishable
4) Pea physiology lends itself to genetic analyses
5) Each plant could be easily mated and this mating could be well controlled (allowing for certainty of parentage)

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7
Q

Character

A

A heritable feature that varies among individuals

Ex: Flower Color

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8
Q

Trait

A

Each variant of a character

Ex: Red or White (flower color)

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9
Q

7 Characters Observed by Mendel

A

1) Seed Color
2) Seed Shape
3) Pod Color
4) Flower Color
5) Flower Position
6) Stem Length
7) ?? Didn’t write it down

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10
Q

Each character Mendel studied had…

A

2 distinct forms/variants

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11
Q

How did Mendel begin his experiments?

A

True Breeding Lines

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12
Q

True Breeding Lines

A

Plants whose offspring resembles the parent over many generations

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13
Q

How are true breeding lines obtained?

A

Self-Pollination

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14
Q

Pea plants make both…

A

Male and female gametes

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15
Q

Anther

A

The plant part where pollen (male gamete) is kept

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16
Q

Pollen

A

Male plant gamete

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17
Q

Self-Fertilization

A

Pollen from within the same plant enters its own stigma

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18
Q

What was a commonality between the true breeding plants Mendel created?

A

All the true breeding plants he made were HOMOZYGOUS for the give trait that he was isolating/studying

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19
Q

Cross Pollination Process

A

1) Took one pea plant and cut its anthers (removed the male gamete parts –> Preventing self-pollination)

2) Collected some pollen from the other plant in the cross onto a brush

3) Brushed this pollen onto the plant that had its anthers cut to initiate fertilization

4) Waited for the seeds in the plant to mature and then planted the seeds to grow the crossed plants and assess their phenotypes

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20
Q

Hybridization

A

The mating or crossing of 2 true-breeding varieties

–> Producing a hybrid (mixed variety) AKA heterozygote

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21
Q

Mendel’s First Experiment (cross)

A

Cross pollinated true breeding lines with different traits for the same character

–> Produced the F1 generation of plants

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22
Q

P Generation

A

Parental Generation (True breeding parents)

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23
Q

F1 Generation

A

First Generation derived from P generation

–> The hybrid offspring of the true breeding P-generation

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24
Q

Results of Mendel’s First Experiment (flower color trait)

A

Crossed true breeding pea plants with purple flower to plants with white flowers

Result –> All offspring had purple flowers (white trait “disappeared”)

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25
Q

Mendel’s Second Experiment (cross)

A

Cross pollinated and allowed for self pollinated of plants in the F1 generation

–> Produced the F2 generation

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26
Q

F2 Generation

A

2nd generation derived from P-generation

–> Made through crossing F1 plants

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27
Q

Results of Mendel’s Second Experiment (flower color trait)

A

The offspring had a ratio of 3 (purple) : 1 (white)

–> The white trait had “reappeared”

28
Q

Mendel coined the terms…
And their initial definitions were…

A

Dominant = Trait observed in F1
Recessive = Trait that “disappeared” in F1

29
Q

Mendel’s Model

–> The idea of heritable factors

A

For each character, an organism inherits 2 versions (alleles) of a heritable factor (gene), one from each parent

30
Q

Mendel’s Model

–> The idea of versions of characters

A

There exists alternative versions of each heritable factor

–> Alleles

31
Q

Alleles account for _____ of inherited characters

A

variation

32
Q

Mendel’s Model

–> The idea of alleles differing at a locus

A

If the 2 alleles at a locus differ, then ONE (dominant allele) determines the organism’s appearance and the OTHER (recessive allele) has no noticeable effect on appearance

33
Q

Dominant

A

Trait that is always expressed when present

34
Q

Recessive

A

Trait that gets masked by the presence of the dominant form

35
Q

Mendel’s Law of Segregation

A

During gamete formation, the 2 alleles of each gene segregate and end up in different gametes

–> Thus, each gamete has ONE allele (of the two present in a diploid) of each gene

36
Q

What does Mendel’s Law of Segregation account for?

A

Meiosis: Specifically, Anaphase I (in which homolog separation occurs)

37
Q

Mendel’s Model

–> The role of fertilization

A

When fertilization occurs, the zygote receives ONE unit from each parent, restoring the pair

38
Q

Homozygous

A

Having a pair of identical alleles

(Homozygote)

39
Q

Heterozygous

A

Having 2 different alleles for a given gene

(Heterozygote)

40
Q

Monohybrid Cross

A

A cross between 2 heterozygotes (both heterozygous for the same character)

41
Q

Phenotype

A

Outward appearance (looks)

42
Q

Genotype

A

Genetic Makeup (the genes)

43
Q

Phenotype ration does NOT always equal the

A

Genotype ratio

44
Q

An organism’s phenotype doesn’t always reveal its…

A

genotype

–> Especially in determining between homozygous dominant and heterozygous (usually have the same phenotype)

45
Q

Test Cross

A

A cross of an organism with UNKNOWN genotype with a HOMOZYGOUS RECESSIVE organism

46
Q

Purpose of Test Crosses

A

Used to determine if an individual exhibiting a dominant trait is homozygous or heterozygous for that trait

47
Q

Test Cross:

Meaning of all offspring being dominant phenotype

A

Means that the unknown genotype is HOMOZYGOUS DOMINANT

48
Q

Test Cross:

Meaning of 1/2 offspring = dominant phenotype and 1/2 = recessive phenotype

A

Means that the unknown genotype is HETEROZYGOUS

49
Q

Dihybrid Cross

A

A cross between two individuals that are heterozygous for TWO characters

–>EX: YyRr x YyRr

50
Q

What did Mendel use the dihybrid crosses for?

A

To test whether traits segregated independently or dependently from one another

51
Q

Mendel’s Law of Independent Assortment

A

2 or more genes assort independently

–> Each pair of alleles segregates independently of any other pair of alleles during gamete formation

52
Q

Exceptions to Mendel’s Law of Independent Assortment

A

Only applies to genes on DIFFERENT, NON HOMOLOGOUS chromosomes or those that are far apart on the same chromosome

–> Genes Located near each other on the same chromosome tend to be inherited TOGETHER*

53
Q

What does Mendel’s Law of Independent Assortment account for?

A

Meiosis –> Metaphase I

–> There is random assignment of chromosomes (homologous pairs have 2 potential orientations and the orientation they end up is random)

54
Q

Punnet Square

A

A diagnostic device for predicting the allele composition of offspring from a cross between individuals of known genetic makeup

55
Q

Each square of a punnet square represents…

A

An EQUALLY PROBABLE fertilization product (assuming random fertilization)

56
Q

Purpose of Punnet Squares

A

Predicts the outcome of a genetic cross

57
Q

Probability Rules:

0 –> 1 Rule

A

Probability scales range from ZERO to ONE

58
Q

Event that is CERTAIN to occur…

A

Probability = 1

59
Q

Event that is certain NOT to occur (impossible)…

A

Probability = 0

60
Q

The probabilities of all possible outcomes for an event must…

A

add up to ONE

61
Q

Probability Rules:

event/Total

A

The probability of an event occurring is the # of time that event could occur over ALL possible events (total)

62
Q

Probability Rules:

What is the probability of pulling the ace of spades out of a deck of cards?

A

1/52

Ace of spades has one occurrence in a deck

A deck has 52 cards total

63
Q

Probability Rules:

Previous Trials Rule

A

The outcome of any Independent event is NOT affected by previous trials

–> Doesn’t matter what happened in the past

64
Q

Product/Multiplication Rule

A

To determine the probability of one event AND another occurring in combination

–>***we multiple the probability of one event by the probability of the other event

(Prob Event #1) x (Prob Event #2) = Prob. of Independent Events Occurring Together

65
Q

Sum/Addition Rule

A

To determine the probability that any ONE of two or more mutually exclusive events will occur

–> The probability that one event OR the other will occur

–>Add the probability of each individual event together

(Prob Event #1) + (Prob Event #2) = Prob. that one or the other will occur