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Evolution and Genetics > Task 2 > Flashcards

Task 2 Flashcards

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Biology 101 flashcards
1
Q

What are single gene characteristics?

A

The difference in a phenotype is determined by which allele the individual has at just one genetic locus

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2
Q

What are polygenic characteristics?

A

Characteristics where variation in the phenotype is related to which allele is present across a number of genes (e.g. height)

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3
Q

What two approaches are there to hunt genes?

A
  1. Linkage studies

2. Association studies

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4
Q

What is the Huntington’s disease?

A

Incurable neurological condition, which leads to the gradual loss of coordination and cognitive abilities
-> single gene disease

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5
Q

How did Mendel’s experiment look like?

A
  1. He established pure yellow- and pure green podded lines of pea plants
  2. He then crossbred both traits which led to the so called F1 generation
  3. After carefully examining their phenotypes he interbred the F1’s which led to a new generation called F2 whose phenotypes he again carefully recorded
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6
Q

What were the results of Mendel’s pea experiments?

A

The F1 generation were all yellow! In the F2’s 3/4 were yellow and 1/4 was green.
3:1 ratio

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7
Q

What did Mendel conclude from his experiments?

A
  1. Each individual must be carrying two particles of heredity from each parent
  2. These particles can either be “green” or “yellow” in form
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8
Q

What are the four points that make up Mendel’s Model?

A
  1. Alleles - alternative versions of genes account for variations in inherited characters
  2. For each character an organism inherits two alleles, one from each parent
  3. Dominant and recessive alleles
  4. Law of segregation
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9
Q

What is Segregation?

A

Seperation of an individuals two genes at a locus into its offspring

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10
Q

What is independent segregation?

A

Phenotypic traits cotrolled by different genes can become separated from each otherthrough generations; therefore, under independent segregation novel combinations of phenotypes are generated even though those traits were not visible in F1
-> when two genes reside on different chromosomes

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11
Q

What is dependent segregation?

A

When the loci are linked on the same chromososme, they do not segregate independently

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12
Q

What does the law of segregation state?

A

During gamete formation (meiosis), the alleles for each gene segregate from each other so that each gamete carries only one allele for each gene.

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13
Q

What does the law of independent assortment state?

A

Each pair of alleles segregates independently of each other pair of alleles during gamete formation

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14
Q

What does the law of dominance state?

A

Some alleles are dominant while others are recessive

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15
Q

What are the four exceptions of Mendelian law?

A
  1. Co-dominance
  2. Incomplete dominance
  3. Mutliple alleles
  4. Pleitropy
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16
Q

How does co-dominance build an exception to the Mendelian law?

A

Heterozygotes fully express the phenotype of both of their homozygous parents (e.g. human blood groups AB)

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17
Q

What does incomplete dominance show?

A

The phenotype of the heterozygote is intermediate in form between those of the two homozygotes (e.g. pink flowers)

18
Q

What is Pleiotropy?

A

One gene is able is able to affect multiple phenotypic characters (e.g. cystic fibrosis and sickle-cell disease)

19
Q

What did Hardy-Weinberg show?

A
  1. The population frequencies of alleles do not change over the generations, even though sexual reproduction is constantly shuffling the combinations up
  2. As long as mating is largely random, the expected frequency of homozygotes and heterozygotes is predictable from the frequency of the allele in general
20
Q

What does the Hardy Weinberg equilibrium show?

A

allele and genotype frequencies in a population will remain constant from generation to generation in the abscence of other evolutionary influences

21
Q

What are the ideal conditions for the Hardy Weinberg equilibrium?

A
  1. No mutations
  2. Random mating
  3. No natural selection
  4. Extremely large population
  5. No gene flow
22
Q

What is the Genetic Drift?

A

In smaller populations random events are more likely and the allele frequencies will fluctuate from generation to generation, even in absence of natural selection due to change;

23
Q

What is the Neutral Theory of Molecular Evolution?

A

Holds that at the molecular level most evolutionary changes and most of the variation withing and between species is not caused by natural selection but by genetic drift of mutant alleles that are neutral

24
Q

What does the Molecular clock show?

A

The more difference there is between DNA sequence of two animals the greater time since their common ancestor

25
Q

What are quantitative genetics?

A

The study of the inheritance of traits that show a continuous distribution in the population. Such traits are not either/or but continuous.

26
Q

What are continuous characters?

A

Characteristics that vary continuously, and every individual in the population differs slightly from every other individual

27
Q

What is the central idea of quantitative genetics?

A

Some of the variance in the phenotypic characteristics is due to the influence of the environment and some is due to the influence of genotype

28
Q

What is the total phenotypic variation?

A

Sum of the genetic variation + environment variation

29
Q

How can we calculate heritability?

A

Divide by 2 each generation in diploid organisms

30
Q

What are the three parameters of the ACE model?

A 
A=  Heritability
C= Shared environment influences 
E= Non-shared environmental influences
31
Q

What are the four problems with twin studies?

A
  1. The environment might not be 100% identical
  2. Parents might treat their MZ twins more similarly than they do their DZ twins and this could cause the MZ twins to become similar
  3. The prenatal environment of MZ twins (shared placenta) could be more shared on average than that of DZ twins (C is often underestimated in a twin study)
  4. After birth MZ twins are usually more dissimilar because they had to compete for nourishment in the womb.
32
Q

What are the three problems with adoption studies?

A
  1. Children are often selectively placed in families which could affect the generalizability of C
  2. Adoption agencies tend to place children in families that seem similar to the child or its biological parents
  3. If adoption occurs immediately after birth, the prenatal environment is of often underestimated and A is overestimated
33
Q

What are dominance effects?

A

Effects are due to interaction between the pair of alleles at the locus

34
Q

What are epistatic effects?

A

Effects due to interaction between alleles at different loci

35
Q

What six explanations does the article by Maher give for the ‘missing heritability’?

A
  1. Right under our Nose
  2. Out of Sight
  3. In the Architecture
  4. In Underground Networks
  5. The Great Beyond
  6. Lost in Diagnosis
36
Q

Explain the first ‘right under our Nose’ point out of the Maher article

A

The GWAS are limited -> they only identify Single Nucleotide Polymorphism that occur in a disease or trait in many individuals
- SNPs represent a much bigger block of genetic material

37
Q

Explain the second ‘out of sight’ point out of the Maher article

A

Screening for common variation delivered less than hoped -> some might be rare not to be found at some point

38
Q

Explain the third ‘in the architecture’ point out of the Maher article

A

Copy-Number Variations (CNVs) could account for the differences between individuals with a disorder and missing heritability; such variations can be base pairs that are deleted or duplicated

39
Q

Explain the fourth ‘in underground networks’ point out of the Maher artile

A

Most genes work together, and it is possible that effects of one on heritability cannot be found without knowing the effects of the other -> Epistasis

40
Q

Explain the fifth ‘the great beyond’ point out of the Maher article

A

Environmental factors that could for example contribute to height are sometimes overlooked (ex: nutrients or toxins)

41
Q

Explain the sixth ‘lost in diagnosis’ point out of the Maher article

A

Medicine tries too hard to squish together a complex collection of symptoms

42
Q

What are the top 10 replicated findings from behavioral genetics acording to Plomin?

A
  1. All psychological traits show significant and substantial genetic influence
  2. No traits are 100% heritable
  3. Heritability is caused by many genes of small effect
  4. Phenotypic correlations between psychological traits show significant and substantial genetic mediation
  5. The heritability of intelligence increases throughout development
  6. Age-to-age stability is mainly due to genetics
  7. Most measures of the “environment” show significant genetic influence
  8. Most associations between environmental measures and psychological traits are significantly mediate genetically
  9. Most environmental effects are not shared by children growing up in the same family
  10. Abnormal is normal

Evolution and Genetics (3 decks)

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