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bio: genetics > quiz #2 > Flashcards

quiz #2 Flashcards

1
Q

Chromosome

A

Each chromosome in a pair codes for the same genetic trait but they provide different details

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2
Q

Genes

A

A segment or band on a chromosome that determines a particular characteristic. Each gene has different possible forms called alleles.

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3
Q

Alleles

A

Gene: eye colour
Possible alleles: brown or not brown
(Different versions of the gene)
-since we have different chromosomes, we have pairs of alleles that determine a particular characteristic
-one of the two alleles is dominant over the other

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4
Q

The dominant allele

A

Represented by a capital letter (B) and is always represented in the physical characteristics of the individual (if present)

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5
Q

The recessive allele

A

Represented by a lower case letter (b) and is only represented in the physical characteristics of the individual if the dominant allele is present

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6
Q

Dominant alleles

A
  • brown eyes (B)

- dark hair (D)

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7
Q

Recessive alleles

A
  • not brown (blue or green) eyes (b)

- blonde hair (d)

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8
Q

The three possible combinations for each pair of alleles…

A
  • BB
  • Bb
  • bb
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9
Q

Homozygous (pure bread)

A
  • an individual in which both alleles are the same
  • homozygous dominant: BB
  • homozygous recessive: bb
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10
Q

Heterozygous (hybrid)

A
  • an individual in which both alleles are different

- heterozygous:Bb

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11
Q

Genotype

A

The genetic makeup of the individual (BB, Bb, or bb)

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12
Q

Phenotype

A

The physical appearance of the individual (brown eyes or blue eyes)
-the homozygous dominant (BB) and heterozygous genotypes (Bb) will have the same phenotype because the dominant allele is present

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13
Q

History of genetics: who is Gregor Mendel?

A
  • father of modern genetics
  • his work was published in 1866, but did not become popular until the 1900’s
  • 1822-1884
  • he was an Austrian monk who used garden pea plants to explain inheritance of characteristics
  • he examined seven different pea traits
  • each trait had only two possible variations (alleles)
  • Mendel was the first individual to propose the principle of dominance, the law of segregation and the law of independent assortment
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14
Q

Mendel’s three major discoveries:

A
  • characteristics/traits are governed by paired but individual factors (genes)
  • these “factors” may be dominant or recessive
  • the factors combine to produce characteristic ratios in the later generations
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15
Q

Principle of Dominance

A

When individuals with different alleles reproduce, the offspring will only express the dominant trait

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16
Q

Law of Segregation

A

Each gene (allele) separates from the other so that the offspring get only one gene from each parent for a given trait

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17
Q

Mendel’s gentil model plants: he worked with peas because:

A
  • they are easy to grow
  • crosses (mated) true breeding peas; pea plants that inherited the same traits generation after generation
  • have many simple traits that distinguish strains of pea plants from each other
  • this includes height (short or tall), seed colour (yellow or green) and seed shape (wrinkled or round)
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18
Q

Test crosses

A
  • mendel’s experiments with pea plants required him to pollinate flowers
  • this refers to as; crossing (fertilizing the flowers reproductive organ)
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19
Q

Generation terms: P

A
  • P generation

- parental

20
Q

F1

A
  • F1 génération
  • first filial
  • the children of P
21
Q

F2

A
  • F2 generation
  • second filial
  • the grandchildren of the P generation
22
Q

Punnet Squares

A
  • chart used by geneticists to determine the probability of results when two individuals are crossed
  • possible gametes produced by the parents are written at the top and side
  • the gametes are combined to produce all of the possible F1 genotypes
23
Q

F2 generation

A

To find the F2 generation, you cross the the offspring produced in the F1 generation
-F2 will always have a genotypic ratio of 1:2:1 (1 homozygous dominant…) and a phenotypic ratio of 3:1 (3 dominant, 1 recessive)

24
Q

Dihybrid cross

A

Involves 2 genes each consisting of heterozygous alleles

25
Q

9:3:3:1

A

Phenotypic ratio when both parents are heterozygous

26
Q

Inheritance patterns

A

If genes are located on separate chromosomes they will be inherited independently of one another
-traits are passed down independently

27
Q

Solving Dihybrid Problems

A
  1. Parents’ genotypes
  2. Possible allele combinations (possible gametes)
  3. Punnet square cross
  4. Ratios
28
Q

Complete dominance

A

A situation where an allele will determine the phenotype l, regardless of the presence of another allele

29
Q

Incomplete dominance

A
  • in between
  • blending
  • neither wants to be dominant
  • a situation where neither allele dominates the other and both have an influence on the individual; results in partial expression of both traits
30
Q

Codominance

A
  • cooperating
  • both want to be dominant
  • a situation where both alleles are expressed fully to produce offspring with a third phenotype
31
Q

3 blood type alleles

A
  • I^A
  • I^B
  • i
32
Q

The 4 blood types and their genotypes

A
  • A: I^A I^A or I^A i
  • B: I^B I^B or I^B i
    AB: I^A I^B
    O: ii
33
Q

Which blood types demonstrate dominant and codominant traits

A

-human blood

34
Q

Pedigrees

A
  • diagrams that illustrate the genetic relationship among a group of related individuals
  • the genotypes are determined by the phenotype
  • using pedigrees and Mendelian genetics, we can determine whether a particular trait is caused by dominant, recessive, autosomal or sex linked allele
  • experimental crosses are not possible in humans
  • medical, historical and family records can be evaluated to study crosses that have already occurred
  • records from several generations can be assembled to form family pedigrees
  • when writing genotypes put both options
35
Q

Pedigree symbols

A
  • mating line
  • offspring line
  • sibling line
  • Roman numerals represent generations
  • numbers represent individuals within a generation
  • the sibling line is in order from oldest (left) to youngest (right)
  • solid symbols indicate that they exhibit the trait of interest- it does not always mean that the trait is dominant
36
Q

Dominant traits in pedigrees

A
  • will be present in each generation

- an individual that represents a dominant trait will have at least one parent that exhibits that dominant trait

37
Q

Recessive traits in pedigrees

A
  • aren’t always present in each generation
  • an individual that exhibits a recessive trait does not have to have a parent exhibit that trait (both parents will be heterozygous carriers of that trait)
38
Q

Chromosomes

A
  • different organisms have different numbers of chromosomes

- humans have 1 pair of sex chromosomes (X or Y) and 22 pairs of autosomes (non sex chromosomes)

39
Q

Autosomal inheritance

A
  • when an allele for a trait is found on an autosome

- males and females affected equally since there’s no difference between autosomes of males and females

40
Q

Sex linked inheritance

A

Alleles causing genetic disorders found on X and Y chromosomes (sex chromosomes)

  • females (XX)
  • males (XY)
41
Q

X and Y Chromosomes

A
  • sections of the X and Y chromosomes are homologous

- however few genes (alleles) are common to both

42
Q

X linked disorders

A
  • phenotypic expression of an allele that is found only on the X chromosome
  • a recessive allele for a disorder located on the X chromosome is more likely to express itself in males than females
43
Q

A male inherits X chromosome from his mother who carries the recessive allele:

A

He will express the disorder because the Y chromosome cannot mask the effects of that allele

44
Q

Males cannot inherit an X linked disorder from father because:

A

Fathers only pass on Y chromosomes to sons

45
Q

Females must inherit two copies of the recessive allele (one on each of the X chromosomes):

A

In order to express the disorder

46
Q

Y-linked disorders

A
  • passed from father to son only
  • fewer Y linked disorders than X linked because Y chromosome is small and does not carry as much genetic info as X chromosome
  • ex: hemophilia, colour blindness, duchenne muscular dystrophy
47
Q

Representing sex linked chromosomes

A
  • males (XY)
  • females (XX)
  • pick a letter to represent the gene
  • establish what is dominant and what is recessive

bio: genetics (4 decks)

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