Week 2

Question 1

What does the P value really mean?

Answer 1

The P value is the probability of a departure form the null expectation that is greater than or equal to what was observed

Question 2

Autosomal Inheritance in Humans

Answer 2

Transmission of genes carried on autosomes

Question 3

What is an autosome

Answer 3

Chromosomes found in both males and females

Question 4

Pattern of inheritance for autosomal dominant traits

Answer 4

• Equal or similar frequency in males and females
• Each individual with the trait has at least one parent with the trait
• Either sex can transmit the trait to an offspring
• Even if both parents have the trait, they may produce offspring who do not have it
• Parents with a dominant phenotype that produce offspring with recessive phenotype must be heterozygous

Question 5

Pattern of Inheritance for autosomal recessive traits

Answer 5

• Equal frequency in males and females
• If both parents have the trait, all offspring also will have it
• The trait is often not seen every generation but frequently seen among siblings in the same generation
• Unaffected parents of offspring with a recessive phenotype must be heterozygous

Question 6

Diploid- Dominant life cycle

Answer 6

Majority of time spent as a diploid, Short period of time spent as haploid (gamete)
- Humans

Question 7

Haploid-Dominant Life Cycle

Answer 7

• Spend majority of life cycle as haploid
• Most fungi and some unicellular eukaryotes

Question 8

Species with blended diploid-dominant and haploid-dominant life cycles

Answer 8

• Some algae and all plants have multicellular diploid (sporophyte) and haploid (gametophyte) life stages
• In seeded plants, the gametophyte stage is only a few cells; the female gametophyte is contained within the flower

Question 9

Cell Division

Answer 9

Tightly regulated process
- Too little prevents appropriate development and growth
- Too much leads to cancer, morphological anomalies and death

Question 10

Mitotic Cell Cycle

Answer 10

• M phase: Cell division occurs
• Interphase: Longer period between cell divisions, including chromosome replication
• G0: Cell division is arrested; cell remains specialized but no longer divides and eventually dies (apoptosis)

Question 11

Stages of interphase

Answer 11

• G1: Active gene expression and cell activity; preparation for DNA synthesis
• S Phase: DNA replication and Chromosome duplication
• G2: Preparation for cell division

Question 12

Nucleolus

Answer 12

Where ribosome subunits are assembled

Question 13

Centrosome

Answer 13

An organelle where spindle fibers form, that contains two microtubule structures called centrioles

Question 14

Kinetochore

Answer 14

A disc-shaped structure where spindle fibers attach to pull sister chromatids apart

Question 15

Prophase

Answer 15

Chromosomes condense

Question 16

Prometaphase

Answer 16

Microtubules attach to chromosomes; nuclear membrane breaks down

Question 17

Metaphase

Answer 17

Chromosomes align on the metaphase plate

Question 18

Anaphase

Answer 18

Sister chromatids seperate

Question 19

Telophase

Answer 19

New nuclear membranes form

Question 20

Cytokinesis

Answer 20

The process by which the daughter cells separate

Question 21

Purpose of cell cycle checkpoints

Answer 21

• Loss of cell cycle control is a major cause of cancer
• Failure of checkpoint leads to programmed cell death (apoptosis)

Question 22

Cell Cycle Check points

Answer 22

• G1 Checkpoint: Pass if cell size is adequate, nutrient availability is sufficient, and growth factors are present
• S-Phase Checkpoint: Pass if DNA replication is complete and has been screened to remove base-pair mismatch or error
• G2 Checkpoint: Pass if cell is adequate and chromosome replication is successfully completed
• Metaphase Checkpoint: Pass if all chromosomes are attached to mitotic spindle

Question 23

Meiosis

Answer 23

• Begins with diploid precursor cell that was generated by mitosis
• Chromatids are then duplicated, but remain connected to each other at the centromere
• The first round of cell division occurs (meiosis I), which results in each homologous chromosome becoming isolated in a different cell
• The second round of cell division occurs (Meiosis II), which results in each chromatid becoming isolated in a different cell (gametes)

Question 24

What three major events occur in Meiosis I

Answer 24

1. Homologous chromosome pair
2. Crossing over (recombination) occurs
3. Homologous chromosomes separate to daughter cells

Question 25

Meiosis: Prophase I

Answer 25

Homologous chromosomes pair (synapsis) and recombine

Question 26

Meiosis: Metaphase I

Answer 26

Pairs of homologous chromosomes align at the metaphase plate

Question 27

Meiosis: Anaphase I

Answer 27

Chromosomes separate; sister chromatids remain attached

Question 28

Meiosis: Telophase I

Answer 28

The nuclear membrane reforms; Cleavage furrow appear

Question 29

Meiosis: Cytokinesis

Answer 29

The process by which cells seperate

Question 30

Meiosis II

Answer 30

Separates sister chromatids into separate daughter cells

Question 31

Recombination

Answer 31

- Occurs between non-sister chromatids of homologous chromosomes - Occurs prior to homolog separation during meiosis I

Question 32

The Synaptonemal Complex

Answer 32

A protein structure that forms between homologous chromosomes during meiosis I in eukaryotes - Mediates recombination

Question 33

How does meiosis relate to the law of segregation?

Answer 33

Homolog separation in meiosis II is the biological basis of segregation

Question 34

How does meiosis relate to the law of independent assortment?

Answer 34

In meiosis one, there are alternative combination of which of the homologous chromosomes goes into each gamete

Question 35

Differences in Oogenesis and Spermatogenesis

Answer 35

- Each miotic cell division of oogenesis results in 1 egg + 2 (or three) polar bodies (unequal cell division) - Each cell division of spermatogenesis results in four sperm cells (equal cell division) -Eggs are non-motile, sperm is motile - Growth phase in spermatogenesis is short (about 70 days), long in oogenesis (years) - Millions of sperm are produced each day - One egg is produced each mensural cycle, 1 ejaculate contains 200-300 million sperm

Question 36

Oogenesis in Humans: Numbers of Oocytes throughout development

Answer 36

- Primary oocytes are established in female fetuses by 20 weeks after fertilization - At this point, there are 7 million primary oocytes - By birth, the number of primary oocytes decreases due to degeneration to 1-2 million (by puberty there are 60,000 - 80,000) - About 500 mature oocytes are produced during a woman's life

Question 37

Oogenesis in humans: formation of an egg

Answer 37

IN UTERO - Oogonium undergoes mitosis to become primary oocyte (which is stuck in prophase I) AFTER PUBERTY - Meiosis I occurs forming secondary oocyte and first polar body - Secondary oocyte undergoes meiotic arrest in metaphase II and ovulation occurs - When fertilized meiosis II is induced creating fully developed egg and secondary polar body

Question 38

Types of zygosity

Answer 38

- Homozygous: Alleles are same - Heterozygous: Alleles are different - Hemizygous: Only one allele (e.g men at most x-linked genes)

Question 39

What is a reciprocal cross?

Answer 39

- Allows one to examine the effects of sex on phenotypes - Uses concept that males have only one X chromosome so they will express recessive phenotypes for x-linked genes even though they have only one recessive X-linked allele - Cross of a female with recessive phenotype and male with dominant phenotype and then compare results to cross of reverse