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Genetics > Chapter 3 > Flashcards

Chapter 3 Flashcards

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Biology 101 flashcards
1
Q

What is a gene?

A

An inherited factor (region of DNA) that helps determine a characteristic.

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2
Q

What is an Allele?

A

One of two or more alternative forms of a gene (like A or a).

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3
Q

What is a locus?

A

A specific place on a chromosome occupied by an allele/gene.

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4
Q

What is a genotype?

A

Set of alleles possessed by an individual organism (like AA, Aa, or aa)

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5
Q

What is a heterozygote?

A

An individual organism possessing two different alleles at a locus (Aa).

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6
Q

What is a homozygote?

A

An individual organism possessing two of the same alleles at a locus (AA or aa).

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7
Q

What is a phenotype or trait?

A

The appearance or manifestation of a characteristic.

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8
Q

What is a characteristic/character?

A

An attribute or feature possessed by an organism.

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9
Q

What is Dominance?

A

One dominant allele (A) can “hide” the phenotype of a recessive allele (a).

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10
Q

What is a dominant allele?

A

Mask the effect of the other alleles (capital letter, like A).

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11
Q

What is a recessive allele?

A

An allele whose effect is masked (small letter, like a).

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12
Q

What is True-breeding?

A

Both alleles are the same (same as homozygous).
-Homozygous dominant (AA)
-Homozygous recessive (aa)

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13
Q

What is the difference between cross-fertilizing and self-fertilizing?

A

In cross-fertilization, there are two different organisms. In self-fertilization, it is the same organism.

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14
Q

What is a Filial (F1 and F2)

A

The generations after the parent generation.
P= parental, first generation
F1= second generation
F2= third generation

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15
Q

What is a testcross?

A

If you have an organism with a
dominant phenotype, but you don’t know the genotype, you cross it with a known genotype (usually homozygous recessive) to determine the unknown genotype

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16
Q

What is the Wildtype?

A

The most prevalent allee in a “wild” population (+).

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17
Q

What is the difference between a locus and
an allele?

A

A locus is a place on a chromosome where genetic information encoding a characteristic is located. An allele is a version of a gene that encodes a specific trait.

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18
Q

What is the difference between
genotype and phenotype?

A

A genotype is the set of alleles possessed by an individual organism, and a phenotype is the manifestation or appearance of a characteristic.

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19
Q

When did Gregor Mendel publish?

A

In 1865

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20
Q

What were the keys to Mendel’s success?

A
  • A good model organism
  • Small number of traits examined
  • Easily differentiated characteristics controlled by a single gene
  • His math, counting results, and writing everything down.
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21
Q

What are Monohybrid Crosses?

A

Cross between two parents that
differ in a single characteristic. The hybrid of two individuals with homozygous genotypes which result in the opposite phenotype for a certain genetic trait
*Looking at one trait (gene) at a time

22
Q

What were the 4 conclusions of monohybrid crossing?

A

1: one character is encoded by two genetic
factors.
2: two genetic factors (alleles) separate when
gametes are formed.
3: The concept of dominant and recessive
traits.
4: Two alleles separate with equal probability
into the gametes.

23
Q

What is the Principle of Segregation (Mendel’s first law)?

A

Each individual diploid organism possesses two alleles for any particular characteristic. These two alleles segregate when gametes are formed, and one allele goes into each gamete.

24
Q

What is the Concept of Dominance?

A

When two different alleles are
present in a genotype, only the trait encoded by one of them―the “dominant” allele―is observed in the phenotype.

25
Q

What explains monohybrid crosses?

A

The Principle of Segregation (The symbols in genetic crosses correspond to alleles on chromosomes).

26
Q

What is a Punnett square?

A

A convenient way to trace the
probabilities of particular genotypes/phenotypes occurring
from a particular cross.

27
Q

What is probability?

A

The likelihood of the occurrence of
a particular event. Used in genetics to predict the outcome of a genetic cross

28
Q

What are the two probability rules?

A
  • The multiplication rule
  • The addition rule
29
Q

What is the Multiplication rule?

A

Calculates the total probability of
two or more events that are
dependent on each other.
(Probability of two fours AND
then a five is 1/6x1/6x1/6 =
1/216)

30
Q

What is the Addition rule?

A

The addition rule calculates the total
probability of two or more events that are not dependent on each other.
(The total probability of rolling either a three OR a four is 1/6 + 1/6 =2/6 = 1/3).

31
Q

What is a Dihybrid Cross?

A

Examine two traits (or genes for Mendel) at a time. Led to The Principle of Independent Assortment.
Experimentally, dihybrids are similar to
monohybrid crosses: two plants that are
either homozygous dominant or homozygous recessive for TWO traits are crossed to give an F1 heterozygote. This plant is self-fertilized to give F2 progeny.

32
Q

What is the Principle of Independent Assortment?

A

States that alleles of two or more different genes assort independently from one another

33
Q

What did Sutton do?

A

Chromosomal Theory of Heredity. Sutton explained everything by chromosomes, meiosis, and fertilization.

34
Q

What are the Common Ratios for phenotypes and genotypes?

A

Also common is the 9:3:3:1 ratio, which is a classic Mendelian ratio for dihybrid crosses.

35
Q

What is a Branch Diagram?

A
35
Q

What are the gamete combinations?

A

Total number of combinations that can occur in gametes = 2^n
(n= haploid number of chromosomes). Example that humans have 23 chromosomes, so they have 2^23 gametes.

36
Q

How are the principles of segregation and independent assortment related, and how are they different?

A

Both the principle of segregation and the
principle of independent assortment refer to
the separation of alleles in anaphase I of
meiosis. The principle of segregation says that
these alleles separate, and the principle of
independent assortment says that they
separate independently of alleles at other loci.

37
Q

How is probability of dihybrid crosses found?

A
38
Q

What is statistics?

A

Provides a way to accept or reject hypotheses in an unbiased manner. In other words, we can accept a hypothesis if certain statistical criteria are met.

39
Q

What does the Chi-Square Test determine?

A

It determines the expected numbers based on hypothesis.

40
Q

What is the Chi-Square Goodness of Fit?

A

Indicates the probability that the difference between observed and expected values is due to chance.

41
Q

When do the Observed and Expected values of a Chi-Square test match?

A

When the x^2 value is to the left of 0.05.

42
Q

When do the Observed and Expected values of a Chi-Square test not match?

A

The more the x^2 value is less than 0.05

43
Q

What are the steps of a Chi-Square problem?

A

First find the x^2 value, then find the degrees of freedom (n-1). Then determine the level of significance with these values and the chart.

44
Q

How is the expected value found in Chi-Square Test?

A

Multiplying the ratio of the expected proportion to the total number observed.

45
Q

What is a pedigree?

A

Pictorial representation of a family history, a family tree that outlines the inheritance of one or more characteristics

46
Q

What is a proband?

A

The person from whom the pedigree is initiated.

47
Q

What is an Autosomal dominant trait?

A

AA or Aa would be affected and aa would not be affected. Aa is the more common genotype of someone with the condition. Examples are Huntington’s disease, Waardenburg syndrome.

48
Q

What is an Autosomal recessive trait?

A

AA would be unaffected, two normal alleles. Aa would be a carrier, with one affected allele. aa would be an affected individual. Examples include sickle cell anemia, cystic fibrosis, albinism.

49
Q

What is the difference between sex-linked and autosomal traits?

A

Sex-linked traits are due to genes that occur on the chromosomes that determine sex, while autosomal traits are due to genes that occur on any of the other chromosomes

50
Q

What are the symbols used in a pedigree?

A
51
Q

How are relationships shown in a pedigree?

A

Genetics (23 decks)

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