Reproductive 1

Question 1

is reproductive system necessary for survival

Answer 1

no, but needed for survival of species

Question 2

provides biological variation by the merging of parental chromosomes

Question 3

how many pairs in humans

Answer 3

23 pairs chromosomes

• 22 pairs - autosomes
• 1 pair- sex chromosomes

Question 4

cell divison -somatic

Answer 4

replace dead/injured cells and add new ones during tissue growth

Question 5

cell division -reproductive

Answer 5

produces gametes (spermatozoa in males and ova in females )

Question 6

primary reproductive organs males and females

Answer 6

gonads :
males - testes
females - ovaries

Question 7

dual function of primary reproductive organs

Answer 7

• gametogenesis to produce gametes
• secrete sex hormones

Question 8

what happens when gametes unite

Answer 8

fertilization -> resulting zygote (ovum and sperm combined) which contains one sex chromosome from each parent

Question 9

maternal

Answer 9

(from mother)

Question 10

paternal

Answer 10

from father

Question 11

in humans how many chromosomes do we have

Answer 11

46 total = diploid (46n)
-> diploid = two copies of each chromosome
23 chromosomes = haploid (23n)
-> haploid = one copy of each chromosome

Question 12

chromatid

Answer 12

each of the strands (sister chromatids)

Question 13

centromere

Answer 13

linking point for sister chromatids (at the centre)

Question 14

Gametogenesis - Spermatogenesis

Answer 14

• primarily begins at puberty
• some spermatogonia remain as precursor
• Mitosis : sister chromatids formed in cell
• Meiosis I : only 1 member of homologous pair per cell
• Meiosis II : homologous seperate; 1 sister chromatid per cell
• Spermatids differentiate to spermatozoa
• 1 spermatogonium poduces 4 spermatozoa

spermatogonia -> (mitosis) -> primary spermatocytes -> (1st meiotic divison) -> secondary spermatocytes -> (2nd meiotic division) -> spermatids -> (differentiation) -> spermatozoa

• after 1st meiotic division there is 23 chromosomes per cell (46 before)
• after 2nd meiotic division there is 1 chromatid per chromosome (2 before)

Question 15

gametogenesis - oogenesis

Answer 15

• begins before birth
• each ovary has a number of primary oocytes
• > at birth 200000 - 2000000
• > at puberty 40000
• > mature to ovulate 400
• most primary oocytes : atresia (cell death)
• meiosis I - not completed till just prior to ovulation; also forms 1st polar body
• meiosis II : completed after fertilization; also forms 2nd polar body
• 1 oogonium produces 1 ovum

oogonium -> (growth/maturation) -> primary oocyte -> (meiosis I) -> secondary oocyte and first polar body ->(meiosis II) -> ootid and secondary polar body -> (differentiation) -> ovum

• 23 chromosomes per cell after 1st meiotic division
• 1 chromatid per chromosome after 2nd meiotic division

Question 16

gameotogenesis - crossing over

Answer 16

• homologous (pair during meiosis; one maternal one paternal) chromosomes align closely
• non-sister chromatids can undergo an exchange of sections (breakage and recombination)
• sister chromatids are no longer identical
• recombinant vs. non-recombinant chromosomes (foreign DNA vs no foreign DNA)
• this allows sexual reproduction to greatly increase genetic diversity
• occurs prior to the completion of meiosis I

Question 17

sex determination

Answer 17

-determined by genetic inheritance of sex chromosomes : X (larger), Y (smaller)
Males : One X and one Y chromosome ->X from maternal and Y from paternal
Females : two X chromosomes -> X from maternal and X from paternal

-presence or absence : SRY gene (sex-determining region of the Y chromosome)

-SRY gene will lead to presence of AMH (anti-mullerian hormone) and testosterone which will give male sexual characteristics.

-They are triggered through sertoli cells and leydig cells in the gonads

Graph*

Question 18

sex differentiation

Answer 18

• multiple processes in reproductive development along male or female lines
• phenotype : sexual appearance and function
• presence or absence : anti-Mullerian hormone, testosterone

Question 19

sertoli cells

Answer 19

produce anti-mullerian hormone (AMH) in primordial gonads

-leads to regression of mullerian ducts in men

Question 20

leydig cells

Answer 20

produce testosterone in primordial gonads

-leads to transformation of wolfian ducts to epididimis, vas deferens, seminal vesicles, ejaculatory duct

Question 21

primary and secondary sexual characteristics

Answer 21

specific physical traits that set apart males and females

-

Question 22

primary sexual characteristics

Answer 22

there from birth (inner and outer genital structures)

Question 23

secondary sexual characteristics

Answer 23

emerge at puberty

-eg. low voices and beards in males/ high voices and no facial hair in females