Bio 1331 - Exam 1 (Meiosis & Genetics)

Front 1

Building up to the Genome

Back 1

Nucleotide (4) --> DNA -- Genes --> Chromosome --> Genome

Front 2

What is a Gene?

Back 2

Basic unit of inheritance that affects phenotype.

Nucleotide sequence that codes for an amino acid sequence.

Front 3

What is an allele?

Back 3

Alleles are the different "versions" of a gene.

e.g. Healthy hemoglobin vs sickle cell hemoglobin. Healthy = ATT; Sickle = ATG

Front 4

How does genotype affect phenotype?

Back 4

Genotype = nucleotide sequence.

The nucleotide sequence codes for an amino acid sequence.

Phenotype = proteins from amino acid sequence.

Front 5

Sexual life cycle

Back 5

Offspring acquire half genes from each parent.

Comes from sperm and egg gametes (haploid n).

Fertilized zygote results (diploid 2n).

Front 6

What is ploidy number?

Back 6

Number of copies of chromosomes.

Humans have 23 pairs. 2n=46 (somatic cells). n=23 (gametes).

Front 7

What are gametes?

Back 7

Gametes are haploid cells that combine to form a new diploid cell. (Sperm and egg).

Gametes are genetically different from another.

Front 8

How are gametes produced?

Back 8

Gametes are produced via meiosis and contain 1/2 the chromosomes as their mother cell and 1/4 the amount of DNA as the cell after S phase.

Front 9

What's the difference between a haploid and diploid cell?

Back 9

A diploid cell has 2 copies of chromosomes.

A haploid cell has only 1 copy of chromosomes.

Front 10

Difference between meiosis and mitosis

Back 10

Meiosis produces gametes to keep ploidy number of offspring same as parents.

Mitosis used to produce somatic cells (skin, neurons, muscle, etc.)

Don't worry about mitosis for this class.

Front 11

What is meiosis?

Back 11

Meiosis is division that leads to a halving of chromosome number (two phases = 1/4 total) and ultimately to the production of gametes.

1 diploid parent cell to 4 haploid daughter cells.

Front 12

Why meiosis?

Back 12

Increase genetic diversity through crossover and recombination.

Front 13

What are the phases of meiosis?

Back 13

Interphase

Prophase 1, Metaphase 1, Anaphase 1, Telophase 1 & Cytokinesis.

Prophase 2, Metaphase 2, Anaphase 2, Telophase 2 & Cytokinesis

Done. Gametes formed.

Front 14

What is interphase?

Back 14

During interphase, chromosomes are duplicated. Each chromosome now consists of two identical copies called sister chromatids.

Front 15

What is prophase?

Back 15

Spindle forms and duplicated centrosomes start to migrate to opposite ends of the cells.

Homologous chromosomes stick together in pairs and do crossover and recombination.

Nuclear envelopes disappears and microtubules from centrosomes stick to chromosomes.

Front 16

What is metaphase?

Back 16

Chromosome pairs are positioned in middle of cell.

Front 17

What is anaphase?

Back 17

Homologous chromosomes separate from each other and move to opposite ends of cell.

Each chromosome still consists of two sister chromatids.

Front 18

What is telophase & cytokinesis?

Back 18

Now 2 daughter cells, with only 23 chromosomes, separate and move from each other.

Front 19

What is Meiosis II?

Back 19

Basically, the whole meiosis I process happens again. Except the result is 4 haploid cells with a single set of chromosomes. These form gametes.

Front 20

What are the changes in ploidy and DNA content during meiosis?

Back 20

DNA content is halved in both meiosis I and meiosis II. Ploidy level changes from diploid to haploid in meiosis I, and remains haploid in meiosis II.

Front 21

What contributes to both genetic variation and heredity? (5)

Back 21

1. Mutations occurring during replication

2. Recombinant chromosomes from crossing over

3. Independent assortment in meiosis I

4. Separation of sister chromatids in meiosis II

5. Random fusion of gametes during fertilization

Front 22

The independent assortment of homologous chromosomes (which are never identical) in meiosis I produces daughter cells that are ___.

Back 22

different

Front 23

What is independent assortment?

Back 23

The alleles for a trait separate when gametes are formed. These allele pairs are then randomly united at fertilization. (Formulated by Mendel.)

Front 24

Black fur in mice (B) is dominant to brown fur (b). Short tails (T) are dominant to long tails (t). What fraction of the progeny of crosses BbTt x BBtt will be expected to have black fur and long tails? (Assume the two genes are located on different chromosomes.)

Back 24

Black fur (BB or Bb) and long tails (tt) will occur in 1/2 (one-half) of the progeny with one-fourth being BBtt and the other one-fourth being Bbtt.

The genotypic outcome of this cross is one-fourth BBTt, one-fourth BBtt, one-fourth BbTt, and one-fourth Bbtt.

Front 25

What are linked genes?

Back 25

If genes are linked, it means that they are on the same chromosome. Linkage is the tendency of particular alleles of different genes to be inherited together.These genes may violate the principle of independent assortment. Linked genes are inherited together unless crossing over occurs between them. When crossing over takes place, genetic recombination occurs.

Front 26

How many different combinations of independent assortment are possible?

Back 26

2^n or 2^number of chromosomes

Humans = 2^23 = Billions of possibilities

Front 27

Where does genetic variation primarily come from? (3)

Back 27

1. Independent assortment

2. Crossover

3. Random fertilization. (Random egg & sperm)

Front 28

What is crossover?

Back 28

During prophase I, homologous chromosomes (1 from mom, 1 from dad) wrap around each other and exchange genetic information.

Front 29

What is independent (random) assortment?

Back 29

Alleles on different chromosomes will assort independently of each other during meiosis.

Because, during metaphase, the chromosomes (mom or dad) can line up in any random order before they are pulled apart.

Front 30

What is random fertilization?

Back 30

A random egg and a random sperm form the zygote.

Front 31

What is an X linked trait?

Back 31

An X linked trait is a trait that can only be passed on the X chromosome. Because females have XX, an X linked recessive can be masked by the extra X. However, males (XY), will express this X linked recessive trait.

Front 32

What is a sex linked trait?

Back 32

A trait carried on the sex chromosomes; either X or Y. Y-linked traits are less common (non-existent in humans) because Y chromosomes are smaller.

Front 33

What is polymorphism?

Back 33

poly = many; morph = type

When two or more phenotypes exist in the same species population.

Example in humans: Sex, blood type, etc.

Front 34

Why was Mendel lucky?

Back 34

He had pea plants with simple genetic traits. (i.e. only two phenotypes, discrete traits, genes were on different chromosomes)

So, no incomplete dominance, or sex linked traits, etc.

Front 35

Incomplete dominance

Back 35

Alleles create intermediate phenotype.

Red + white = pink.

Front 36

Codominance

Back 36

Heterozygotes display phenotypes for both alleles.

MM x NN = MN

Front 37

The ABO blood type of humans is an example of...

Back 37

multiallelic, polymorphic, and complete dominance or codominance

Front 38

In humans, the _#_ blood types are made up of _#_ alleles.

Back 38

4 blood types: A, B, AB, O

3 alleles: i, IA, IB

Front 39

Pleiotropy

Back 39

When a single gene affects more than one trait

Front 40

Epistasis

Back 40

Epistasis is the gene interaction in which a gene (the epistatic gene) can disallow the phenotypical manifestation of another gene.

e.g. Labrador coat color.

Front 41

Micro Evolution

Back 41

Change of allele frequency in a population from one generation to the next

Front 42

Macro Evolution

Back 42

"Descent with modification"

Front 43

(Scientific) Fact

Back 43

An observation that has been repeatedly confirmed.

Front 44

Law

Back 44

A descriptive generalization about how some aspect of the natural world behaves under stated circumstances.

Front 45

Hypothesis

Back 45

A testable statement about the natural world that is falsifiable and can be used to build more complex inferences and explanations

Front 46

(Science) Theory

Back 46

A well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses.

Impossible to prove theory as true.

Is parsimonious = simple.

Front 47

The knowledge hierarchy. Science vs Public.

Back 47

Science: 1) Theories 2) Laws 3) Hypotheses 4) Facts

Public: 1) Facts 2) Laws 3) Theories 4) Hypotheses

Front 48

Is evolution fact or theory?

Back 48

Evolution has both observable facts and testable hypotheses... thus making it a theory.

Front 49

Components of good experiment

Back 49

1) Control group - to check for other factors that might be influencing results

2) Experimental conditions are controlled to eliminate extraneous variables

3) Tests are repeated to reduce effects of random variation

Front 50

Non-Disjunction

Back 50

Error in meiosis.

During 1st phase homologous chromosomes don't separate... trisomy or monosomy.

During 2nd phase sister chromatids don't separate. Less common but happens.

Front 51

Sex are cost/benefits long term or immediate?

Back 51

Benefits are long term.

Costs are immediate.

Front 52

Immediate costs of sexual reproduction

Back 52

1) Recombination-disrupts coevolved genes

2) Meiosis and syngamy-takes longer than mitosis.

3) Ecological costs (predation + diseases)

4) Mate searching

5) Cost of meiosis-asexual females pass on full genetic material. Sexual female loses half.

Front 53

3 Genetic hypotheses:

Back 53

Fisher-Muller Hypothesis

Muller's ratchet

Mutation load

Front 54

Genetic hypothesis to explain sex

Back 54

Fisher-Muller hypothesis.

Sexual species can adapt faster to changing environment. More robust genotype because recombination combines beneficial mutations and adapts faster to selective pressures.

But... most mutations are deleterious.

Front 55

Least Loaded Class

Back 55

Group of individuals with fewest number of deleterious mutations = best.

In sexual, if LLC dies, then it's okay. LLC can be regenerated through recombination.

Front 56

Muller's ratchet

Back 56

With every turn (mutation) of ratchet you can't go back. So they keep accumulating.

Bad for asexual creatures.

Salmonella example.

Front 57

2 Ecological hypotheses to explain sex:

Back 57

Tangled bank hypothesis

Red Queen Hypothesis

Front 58

Tangled Bank Hypothesis

Back 58

Lottery ticket. Have a ton of small offspring to increase genetic diversity and therefore survival chances.

Currently being rejected bc most sexual produce few, large offspring,

Front 59

Red Queen Hypothesis

Back 59

Species "chase each other". At heart concept of co-evolution.

e.g. Rabbit and wolf. Rabbit adapts runs faster to run away. Wolf adapts to run faster too.

Front 60

Principle of segregation

Back 60

i. Genes are located on chromosomes.

ii. Separation of homologous chromosomes during meiosis I explains why alleles of the same gene segregate to different gametes.

Front 61

2 hypotheses to explain inheritance:

Back 61

1) Blending hypothesis

2) Particulate inheritance

Front 62

Blending hypothesis

Back 62

Offsprings phenotype is a blend of their parents. So red + white = orange.

But... rejected. This would lead to homogenous species. Doesn't happen.

Front 63

Particulate inheritance

Back 63

Parents pass on discrete heritable "units" that retain their separate identities in offspring.

Discovered by Mendel.

"Discrete units" now known as genes.

Front 64

Mendelian Dihybrid cross results in what ratio of phenotypes?

Back 64

9:3:3:1

Front 65

Polygentic traits

Back 65

Many genes are involved in phenotype in an additive fashion.

e.g. Human skin color, Human height, Kernel color, etc.

Front 66

Cuvier

Back 66

Classification of animals in 4 branches.

Catastrophism: each boundary between strata represents a catastrophe.

Animals are similar bc performing similar function not common ancestry.

Front 67

Lyell

Back 67

Father of geology and huge influence on Darwin.

Earth is ancient.

Uniformitarianism/gradualism: Changes in Earth's surface result from slow continuous actions still operating today. Slow but cumulative effects.

Front 68

Hutton

Back 68

With Lyell on the whole uniformitarianism/gradualism.

Front 69

Linnaeus

Back 69

Father of taxonomy.

Believed species dispersed when Ark crashed in Turkey.

Front 70

Lamarck

Back 70

Traits gained during lifetime are passed onto offspring.

Front 71

Wallace

Back 71

Co-Founder of natural selection.

Front 72

Evidence of evolution: Change through time (3)

Back 72

1) Extinction (fossils)

2) Transitional Forms

3) Environmental Change

Front 73

Evidence of evolution: Evidence that species are related (3)

Back 73

1) Structural homologies

2) Developmental homologies

3) Genetic homologies

Front 74

Darwin's 4 postulates

Back 74

1) Individuals in populations within species vary

2) Some of these variations are heritable

3) More offspring are produced than can survive

4) Survival and reproduction are nonrandom

Front 75

How many alleles per gene does a normal sperm or egg cell have?

Back 75

Only 1 allele.

You can see 2 alleles at the same time only in diploid cells.

Front 76

What is, basically, a pedigree chart?

Back 76

A family tree

Front 77

Pedigree chart: Which shape is female? male?

Back 77

male = square

female = circle

Front 78

Pedigree chart: What color is an affected person? What color is a carrier?

Back 78

affected person = colored in shape

carrier = half colored in shape

Front 79

Homologous chromosomes separate during Meiosis 1 or 2?

Back 79

1

Front 80

Sister chromatids separate during meiosis 1 or 2?

Back 80

2

Front 81

What is "descent with modification"?

Back 81

What Darwin described evolution as.

Front 82

What did Darwin say about evolution and natural selection?

Back 82

Evolution is a process.

Natural selection is a mechanism.