Human Life Cycle

Question 1

Gametogenesis

Answer 1

The production of gametes

Question 2

Spermatogenesis

Answer 2

Meiosis in males
(diploid cell -> spermatid -> sperm)
Haploid cells grow flagella to be motile

Question 3

Oogenesis

Answer 3

Meiosis in females
(diploid cell -> oocyte -> egg)
Make a single large haploid cell rather than 4 little haploid cells
Discarded cells = polar bodies

Question 4

Spermatogenesis in Humans

Answer 4

Step 1: meiosis
Step 2: maturation
Cells begin entering meiosis at puberty and take 60 days

Question 5

Oogenesis in Humans

Answer 5

Step 1: cells start meiosis in fetus and pause in prophase 1
Step 2: beginning at puberty once a month one or two cells:
-resume meiosis
-enter oviduct
-can be fertilized

Question 6

What is Contributed during Fertilization?

Answer 6

Sperm = 23 paternal chromosomes
Egg = 23 maternal chromosomes + cytoplasm with mitochondria

Question 7

When does DNA replication first occur?

Answer 7

At the zygote stage

Question 8

When do genes turn on?

Answer 8

4-cell stage = zygotic genome activation

Question 9

Cells floating in the amniotic fluid are:

Answer 9

From the embryo - cells from the embryo can be collected via amniocentesis

Question 10

Dizygotic Twins

Answer 10

Two separate eggs are fertilized and implanted in the uterus

Question 11

Monozygotic Twins

Answer 11

Can be made by splitting at the two-cell stage and implanting in separate sacs or by splitting the inner cell mass and implanting in the same sac