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Cell Biology Final Exam > Mendel > Flashcards

Mendel Flashcards

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1
Q

What is the difference between a normal red blood cell and a sickle-cell red blood cell?

A

A normal red blood cell is donut shaped and flexible whereas a sickle cell is partially broken (like a banana) and is not flexible. This means that red blood cells can squeeze their way through the cells on the capillaries to bring oxygen but can’t squeeze through if not flexible. This is all because of one nucleotide that is changed in the gene that codes for the betaglobin protein (affects hemoglobin), leads to the change in the nucleotide sequence, changes structure and function. This is an inherited disease (embedded into the genetic material)

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2
Q

Blending Theory of Inheritance

A
  • Hereditary traits blend evenly in offspring through mixing of parents’ blood
  • E.g a blue parent and a yellow parent make a green child
  • Proven false
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3
Q

What the Blending Theory of Inheritance doesn’t explain

A
  1. Extremes do not gradually disappear

2. Offspring sometimes have traits that differ from both parent (2 parents with brown eyes have a blue-eyed child)

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4
Q

Gregor Mendel

A
  • Founder of genetics- really got us to understand inheritance
  • First to use scientific method to study inheritance
  • Studied theology with science and math
  • Grew up on a farm and understood growing crops to get best traits
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5
Q

Why did Mendel chose the garden pea?

A
  • Easy to grow, cheap
  • Clearly defined characters (flower colour, shape of pod, colour of seed)
  • Variation in character-traits (white or purple, inflated or compressed, yellow or green-no in between)
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6
Q

Genes

A

Characters are passed onto offspring as discrete hereditary factors

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7
Q

True-breeding varieties

A
  • Self-fertilized plant
  • Those plants that if they self-fertilize all of the offspring they produce have the exact same characteristics as the parent
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8
Q

Cross-Pollination

A
  • Cross of two different true-breeding plants that have different traits(white X purple flowers)
  • same and different traits in each generation
  • takes the sperm from one plant (pollen) and transfer it to the egg (the carpel) to fertilize eggs
  • needs to first remove the anther and the pollen from the egg plant
  • seeds are embryos
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9
Q

P generation (Parents)

A
  • plants used in the initial cross
  • each pea produced contains an embryo
  • Purple flowers crossed with white flowers
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10
Q

F1 generation (Filial)

A

First generation
Filial=children or offspring in Latin
all formed purple flowers

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11
Q

F2 generation

A

Second generation

3 purple, 1 white (3:1 ratio)

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12
Q

Mendel’s First Hypothesis

A

Genes for genetic characters occur in pairs

- one gene inherited from each parent

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13
Q

Alleles

A

different versions of a gene

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14
Q

Diploid

A

two copies of each gene

-Mendel laws work only for diploid organisms

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15
Q

Mendel’s Second Hypothesis

A

If two alleles of a gene are different, one allele is dominant over the other

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16
Q

Dominant

A

allele is expressed

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17
Q

Recessive

A

allele is masked

- only expressed when two copies of the allele present

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18
Q

Mendel’s Third Hypothesis

A

Two alleles of a gene segregate (separate) and enter gametes singly

  • half the gametes carry one allele, half carry the other allele (haploid)
  • Principle of Segregation
  • Two gametes fuse to produce to produce a zygote that contains two alleles (diploid)
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19
Q

Homozygous

A
  • Both alleles the same
  • PP (dominant)
  • pp (recessive)
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20
Q

Heterozygous

A
  • two different alleles

- Pp

21
Q

Monohybrid Cross

A

Focus on a single character

-results supports Mendel’s hypothesis

22
Q

Genotype

A
  • Genetic constitution of an organism

- PP,Pp,pp

23
Q

Phenotype

A
  • Outward appearance

- Purple flowers, white flowers

24
Q

Mendel could predict:

A
  • Classes of offspring (how many are purple/white flowers)

- Proportions of those offspring

25
Q

Product Rule of Probability

A
  • Probability of two independent events occurring in succession
  • The independent probabilities multiplied
  • Two heads: 1/2 X 1/2 = 1/4
26
Q

Sum Rule in Probability

A

Probability of two different events producing the same outcome

  • the individual probabilities added
  • probability of heads and tails in two tosses: 1/4 + 1/4
27
Q

Testcross

A

cross an unknown genotype with a homozygous recessive individual
-determines if the unknown is a heterozygote or homozygote

28
Q

Mendel’s Fourth Hypothesis

A

Alleles of genes that govern two different characters segregate independently during formation of gametes

  • Principle of Independent Assortment
  • Due to independent assortment during meiosis
29
Q

Dihybrid Cross

A

Two characters

  • P generation: RRYY x rryy
  • F1 generation: all Rr Yy
30
Q

Rr Yy X Rr Yy

A

9:3:3:1 ratio

31
Q

Rr Yy X rr yy Testcross

A

1:1:1:1 ratio

32
Q

Walter Sutton

A

Parallels between genes and chromosomes in meiosis and fertilization

33
Q

Chromosome Theory of Inheritance

A
  1. Chromosomes occur in pairs in diploid organisms
  2. Chromosomes of each pair are separated and delivered singly to gametes
  3. Independent assortment of chromosomes
  4. Each chromosome of each pair is derived from each parent
34
Q

Locus

A
  • site occupied by a gene on a chromosome

- alleles on different homologous chromosomes have same loci

35
Q

Incomplete Dominant

A
  • dominant allele is not completely dominant over recessive
  • the heterozygote phenotype is different from either homozygote phenotype
  • red X white makes all pink F1: red delivers the red pigment, white enzymes are mutated
  • the dominant gene cannot perfectly mask the nondominant phenotype so some of the white shows through
36
Q

Why is incomplete dominance not blending?

A

Crossing the 2 pink (F1) plants made 1 red, 2 pink, 1 white. If blending occurred they would all be pink

37
Q

Sickle-cell incomplete dominance

A
  • homozygous recessive has sickle-cell disease

- heterozygote has milder sickle-cell trait

38
Q

Familial hypercholesterolemia

A
  • homozygous recessive has severe form of disease

- heterozygote has mild form of disease

39
Q

Tay-Sachs disease

A
  • homozygous recessive has serious symptoms

- heterozygoud has no symptoms but has detectable biochemical effects

40
Q

Codominance

A

Different alleles of gene have equal effects in heterozygotes (both alleles expressed)

  • E.g. human blood types
  • similar inheritance to incomplete dominance (1:2:1)
41
Q

Multiple Alleles

A

More than two types of alleles for a gene
- found among all individuals in a population
- diploid individuals only have 2 of the alleles
Phenotype depends on relationship between different pairs of alleles
- still follows Mendel’s principles
Small differences in DNA sequences result in multiple alleles

42
Q

Antigens

A
  • glycoproteins on surface of RBCs
  • IA allele produces A antigen (dominant)
  • IB allele produces B antigen (dominant)
  • i allele produces neither A nor B (recessive)
43
Q

Blood Types (phenotypes)

A
  • IAIA or IAi= type A blood
  • IBIB or IBi= type B blood
  • ii=type O blood
  • IAIB= type AB blood
44
Q

Human ABO Blood Group

A

Immune system produces antibodies against antigens not found on its own RBC

45
Q

Epistasis

A

Genes interact:

  • allele of one locus inhibits or masks effects of allele at a different locus
  • some expected phenotypes do not appear among offspring
46
Q

Labrador Retrievers (epsistasis)

A

Melanin pigment genes and Pigment deposition gene. —Black lab could be homo dominant or hetero for both genes

  • Brown fur is recessive melanin and dom or hetero pigment deposition
  • Yellow fur is any combo of melanin with recessive pigment deposition
    9: 3:4 ratio
  • E gene is epistatic to B gene, independent assortment
47
Q

Polygenic Inheritance

A

Several genes at different loci interact to control the same character
- produces continuous variation
Phenotypic distribution: bell-shaped curve
Often modified by environmental effects (Quantitative traits)
E.g human height

48
Q

Pleiotropy

A

One gene affects more than one character
Sickle-cell disease
- recessive allele affects hemoglobin structure and function
- leads to blood vessel damage
-damages many tissues, organs, and functions
-many different symptoms result

Cell Biology Final Exam (6 decks)

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