Meiosis & genetics (genetics & inheritance) Part 2 - (Week 8) Flashcards

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1
Q

What generation are the ‘true-breeding parents’?

A

P generation

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2
Q

What is the hybrid offspring of the P generation called?

A

F1 generation

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3
Q

What do we call the offspring of the F1 generation?

A

F2 generation

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4
Q

If two contrasting ‘true-breeding’ white & purple flowered pea plants are bred together, what colour will their offspring be?

A

F1 hybrids (P gen offspring) will all be purple flowers

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5
Q

What colour will the offspring of purple flowered F1 hybrids produce?

A

Flowers purple & white with ratio of 3:1

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6
Q

What does the offspring in F1 & F2 generation of pea plants suggest?

A

Mendel called the purple flower the ‘dominant’ trait and the white flower the ‘recessive’ trait

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7
Q

What are alleles?

A

They are alternative versions of a gene - each gene resides at a specific locus on a specific chromosome

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8
Q

For ‘true-breeding’ parents, what type of alleles do they have?

A

They have alleles at a particular locus that are identical (e.g both dominant/both recessive)

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9
Q

Do alleles in F1 hybrids have alleles at identical or different loci?

A

The two alleles in an F1 hybrid are at loci that are different

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10
Q

Give the 4 main ideas that explain the 3:1 inheritance pattern observed in F2 offspring

A
  1. Alternative versions of genes account for variations in inherited characters
  2. For each character, an organism inherits 2 alleles, one from each parent
  3. If the 2 alleles at a locus differ, then one (dominant allele) determines organism’s appearance, & the other (recessive) has no noticeable effect on appearance
  4. The law of segregation
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11
Q

What is the law of segregation?

A

The 2 alleles for a heritable character separate (segregate) during gamete formation (meiosis) & ended up in different gametes (gametes get only one of the 2 alleles present in the organism)

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12
Q

What does it mean if an organism is ‘homozygous’ for a gene?

A

An organism with two identical alleles for a character is homozygous for the gene controlling that character

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13
Q

What does it mean if an organism is ‘heterozygous’ for a gene?

A

An organism that has two different alleles for a gene is heterozygous for the gene controlling that character

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14
Q

Homozygotes are not true-breeding. True or false?

A

False. Homozygotes are true-breeding, heterozygotes are not

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15
Q

What is meant by the term ‘phenotype’?

A

Physical appearance

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16
Q

What is meant by the term ‘genotype’?

A

Genetic makeup

17
Q

How can we determine genotype?

A

Do a testcross

  1. Breed the mystery individual with a homozygous recessive individual
  2. If any offspring display the recessive phenotype, the mystery parent must be heterozygous
18
Q

What is dihybrid inheritance?

A

Simultaneous inheritance of 2 characteristics

19
Q

Using a dihybrid cross, Mendel developed the Law of Independent Assortment. Describe what the means

A
  • Each pair of alleles segregates independently of each other during gamete formation
  • Applies only to genes on different, non homologous chromosomes or those far apart on the same chromosome
  • Genes located near each other on the same chromosome tend to be inherited together
20
Q

What is the Hardy-Weinberg Principle?

A

It states that the frequency of dominant and recessive alleles will remain constant from generation to generation provided certain conditions exist

21
Q

What are the certain conditions required for the Hardy-Weinberg Principle to be true?

A
  • No selection is taking place (all alleles are equal)
  • No mutations occurring
  • Mating is random
  • Population is large
  • No migration
22
Q

What equation must you use to calculate the frequency of a dominant or recessive allele?

A

p+q = 1.0

p = dominant allele
q = recessive allele
these frequencies are expressed as %, fractions or decimals

23
Q

How can you calculate the frequency of a genotype?

A

p^2 + 2pq + q^2 = 1.0

24
Q

What genotype does p^2 represent?

A

Frequency of the homozygous dominant

25
Q

What genotype does 2pq represent?

A

Frequency of the heterozygous

26
Q

What genotype does q^2 represent?

A

Frequency of the homozygous recessive

27
Q

How do you calculate the chance for various genotypes in a multi character cross?

A
  • A multi character cross is equivalent to 2+ independent crosses occurring simultaneously
  • To calculate chances for various genotypes, consider each separately
  • Multiply each individual probability
28
Q

When does Mendelian inheritance not apply?

A

When:

  • Alleles are not completely dominant or recessive
  • A gene has more than two alleles
  • A gene productes multiple phenotypes

(However the basic principles still apply)

29
Q

What is complete dominance?

A

It occurs when phenotypes of the heterozygote & dominant homozygote are identical

30
Q

What is incomplete dominance?

A

When the phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties

31
Q

What is codominance?

A

Two dominant alleles affect the phenotype in separate, distinguishable ways

32
Q

Give an example of incomplete dominance

A

When two different coloured ‘true-breeding’ parent flowers produce a hybrid offspring with a colour inbetween the two

33
Q

Give an example of codominance

A

Blood groups in humans. There are 3 alleles: IA, IB, i (IA & IB are dominant, i is recessive)