Ch. 3 Flashcards
Mitosis
cell growth, repair, asexual division
2N -> 2N, 2N (diploid)
N= 23 (human)
Meiosis
sexual reproduction (sperm & eggs)
2N -> N, N, N, N (haploid)
N= 23 (human)
Gametes
sperm & oocytes
Gonads
paired structures (testes & ovaries)
Semen
5% sperm + 95% seminal fluid (from seminal vesicle)
Vas deferens
rapid transport of sperm
Epididymis
sperm complete maturation
Testis
contains sperm-producing seminiferous tubules and cells that secrete testosterone and other hormones
Meiosis
Homologous pairs have the same genes in the same order but CARRY DIFFERENT ALLELES (variants) of the same gene
gametes are haploid & somatic cells are diploid for each chromosome
Mitosis
- occurs in body cells
- divides ONCE
- creates TWO cells
- identical
Meiosis
- occurs in gametes cells
- divides TWICE (meiosis I & II)
- creates 4 cells
- NOT genetically identical
- increases genetic diversity
Spermatogenesis
spermatogonium (diploid) - primary spermatocytes (diploid) - meiosis I - secondary spermatocytes (half of diploid #) - meiosis II - acrosome/spermatid (haploid)- sperm accumulate in center (haploid)
Sperm Structure
Acrosome
enzymes to digest surface of egg (in sperm head)
Sperm structure
Head
DNA in enzyme-rich cap
Sperm Structure
Nucleus
In sperm head
Sperm Structure
Spiral Mitochondria
energy to swim
in midpiece
Sperm Structure
Tail
flagella w/ core of microtubules
Oogenesis
Oogonium (diploid) - primary oocyte (diploid) - meiosis I - secondary oocyte OR first polar body may divide (half of the diploid #) - meiosis II (if fertilization occurs) - ovum (egg) & second polar body (haploid) OR polar bodies die - mature egg
During ovulation period, is the ovum primary or secondary?
Secondary
Meiosis I
- homologous chromosomes form pairs
- the # of replicated chromosomes is halved
- two daughter cells are formed
- crossing over occurs
Meiosis II
- 4 daughter cells formed
- sister chromatids separate
Spermatogenesis
- an acrosomal region must be present in mature cells
- 4 gametes are produced that could contribute to zygote
- a mitochondria- containing midpiece must be present in mature cells
Oogenesis
- one gamete is produced
- meiosis is completed only if fertilization occurs
- polar bodies are formed
Oocyte
the largest human cell
A Woman’s Biological Clock
Birth (about 1mil follicles) - Menopause (less than 10k), # of follicles drop at each milestone (birth, puberty, most fertile @ 20, fertility decline @ 35, not healthy oocytes start, menopause)
1 egg per follicle
Fertilization
- fusion of oocyte & sperm
- formation of zygote (fertilized egg)
- formation of blastocyte by cell division (implant to wall of uterus)
- inner cell mass form cells of fetus (embryonic stem cells)
- trophoblast form support structures for fetus (placenta)
Pregnancy
First trimester- organ formation
Second trimester- organ maturation
Third trimester- rapid growth
Zygote
two genetic packages meet & merge
A species has a diploid number of 36. Without meiosis, the gametes would each contain _________blank chromosomes, and the fertilized ovum would have _________blank chromosomes.
36; 72
How many sex chromosomes does a human sperm or egg contain? How many autosomes?
1; 22
What is the molecular mechanism underlying most accelerated aging conditions?
Inadequate DNA repair
Ovulation to Implantation
Day 0: ova duct, ovulated secondary oocyte - fertilization - zygote- uterine tube
Day 1: meiosis
Day 2: 2 cells
Day 3: 4 cells
Day 4: Morula (can divide into multiple for twins)
Inner Cell Mass
Day 7: blastocyst implants (abortion pills thin uterine wall) - embryo
Monozygotic twins
Identical; single fertilized ovum, 3 types can form depending on when fertilized ovum or when embryo splits , exposed to slightly different uterine environments
Dizygotic Twins
Fraternal; two sperm fertilize two oocytes, same genetic relationship as any 2 siblings
Organogenesis
transformation of the simple three germ layers into distinct organs
Fetus growth
soft cartilage to bones, nerve and muscle functions become coordinated, wk 6 = anatomical differences (SRY gene expressed in males), wk 12 = kicks, faces, fists, sucks thumb, 4 month = fetus has hair, eyebrows, etc
Teratogens
chemical or other agents that cause birth defects
Is longevity inherited?
Centenarians have inherited 2 types of gene variants- those that directly protect them and wild type alleles of genes that when mutated causes diseases (complex traits)
