exam 1

Question 1

preformation/uniparental inheritance vs blended inheritance

Answer 1

preformation/ uniparental inhertiance: traits determined by just one parent (female for “ovists”, male for “spermists”)

blended inheritance: offspring merge information from both parents, resulting in a unique blend

prevalent views of inheritance before Mendel
- problem was they lacked explanatory or predictive power

Question 2

walther flemming

Answer 2

• discovered mitosis: “process of threads”
• looked at live salamander tail fin cells
• dyed cells inside nucleus stained vigorously
• called it chromatin

Question 3

Theodor Boveri (1895) and E.B. Wilson (1896)

Answer 3

found that there was something special about the nucleus

• removed nuclei from sea urchin eggs and replaced them with transplanted nuclei
• never grew to adulthood but sometimes eggs with transplanted nuclei were able to hatch into larvae!
• suggests that something in the nuclei (chromosomes) are required for creating an organism

Question 4

eukaryotic chromosomes

Answer 4

are a nucleoprotein complex

• eukaryotic chromosomes have linear DNA molecules associated with large amount of protein
• DNA wrapped around histone proteins
• wrapping and unwrapping is highly regulated

Question 5

chromatin

Answer 5

chromatin, complex of DNA and protein, is found in the nucleus of eukaryotic cells

• during cell division, chromatin condenses to form structures seen by Flemming (not easily visible during interphase, easily visible during mitosis)

Question 6

5 phases of mitosis

Answer 6

Prophase: chromosomes starting to condense, spindle forming

Prometaphase: chromosomes condensed, nuclear envelope breakdown

Metaphase: chromosomes meet at the middle

Anaphase: chromosomes move apart

Telophase: cells start dividing; cytokinesis (separation of 2 daughter cells)

Question 7

Walter sutton (1903)

Answer 7

1. discovered that chromosomes come in pairs
2. via meiosis in gonads, each gametes gets a single member of a chromosome pair: eggs and sperm have half the regular number of chromosomes
3. surmised that during fertilization, the egg and sperm each contribute a member of a chromosome pair, regenerating the full number of chromosomes

Question 8

2 sets of cell divisions in meiosis

Answer 8

meiosis I: separation of homologous chromosomes

meiosis II: separation of sister chromatids

• 2 cell divisions result in 4 daughter cells rather than 2 daughter cells in mitosis
• each daughter cell has only half as many chromosomes as the parent cell

Question 9

nattie stevens (1905)

Answer 9

• used drosophila (fruit flies)
• died of breast cancer early though
• discovered that males have the Y and females have the XX

Question 10

T.H. Morgan (1910)

Answer 10

• discovered sex linkage after discovering and mating the white-eyed male
• concluded that Mendel’s genes reside physically on chromosomes (on the X chromosome)

Question 11

carrier

Answer 11

someone who carries one of the diseased alleles but themselves is not affected

Question 12

Alfred sturtevant +recombinant frequency

Answer 12

stared at Morgan (white eye cross guy)’s data and said that recombinant frequencies are a measure of the physical distance between genes on a chromosome

• mapped distance between genes on chromosomes

recombinant frequency = distance b/w genes

Question 13

chiasmata

Answer 13

X-shaped regions where crossing over occurs

• each tetrad usually has 1 or more chiasmata

tetrad: each pair of chromosomes forms a tetrad, a group of 4 chromatids

Question 14

when do homologous chromosomes cross over

Answer 14

in prophase I

crossing over: non sister chromatids exchange DNA segments

Question 15

importance of sexual reproduction + 3 important contributing factors

Answer 15

creates genetic variation because of:
- independent assortment of chromosomes
- random fertilization
- crossing over (recombination)

Question 16

bacterial chromosome

Answer 16

is a double stranded, circular DNA molecule associated with a small amount of protein

• DNA is “supercoiled” and found in the nucleoid region