DEVELOPMENTAL BIOLOGY Flashcards
(40 cards)
what is the study of developmental biology
the study of growth and differentiation.
what is epigenesis
all the organs are formed “de nevo” (from new) as the embryo develops
what is gametogenesis
the formation of gametes generated by meiosis. In males, spermatogenesis and females oogenesis
what are the basic results of meiosis
meiosis halves the chromosome number and produces 4 haploid cells
what are the steps and descriptions of meiosis
interphase: only occurs once, DNA replication, sister chromatids form making diploid number
prophase 1: Homologous chromosomes undergo synapsis and join at the chiasmata. Mitotic spindle forms, recombination occurs
metaphase 1: line across equator, teathered by mitotic spindles
anaphase 1: Homologous chromosomes separate, Sister chromatids remain attached.
telophase 1 + cytokenesis: start to cleave, splits into 2 cells
2: all occur the same except no recombination, crossinfg over and the sister chromatids are split into 2 more cells to create 4 haploid daughter cells.
what part of meiosis is most like mitosis
meiosis 2
what is independent assortment
where chromosomes line up differently along the equator. left side may not just be paternal chromosomes and this leads to genes segregating independently during gamete formation.
what is crossing over and recombination
genes become shuffled in prophase 1 and metaphase 1 between non sister chromatids attaching, swapping genetic information to make new combinations on the initial chromosomes.
outline Mutations in DNA
point mutations (1 nucleotide), deletions, duplications, copy number variation. Common mutations that are not deleterious are called polymorphisms and are not usually harmful. Mutations are key to genetic evolution and variation.
what are sertoli cells
somatic cells that supply key signals to support, nurse the germ cells.
what are oogenia, oocyte, ovum
oogonia: diploid precursor cell that gives rise to oocyte
oocyte: haploid egg cell
ovum: mature oocyte that has been released from ovary ready for fertilisation.
outline oogenesis
oogonia divide by mitosis to produce oocyte then arrest at prophase 1
At puberty follicle stimulating hormone causes follicles, oocyte, to mature into a secondary oocyte by meiosis and then arrest again at metaphase 2.
meiosis 2 resumes when penetrated by sperm to produce a fertilised egg
differences in gametogenesis males and females
common: morphological differentiation between stages. Do not survive long without fertilisation
differences: spermatogenesis produces 4 equivalent gametes whereas oogenesis produces 1 mature ovum and 3 polar bodies
different timing of maturation. spermatogenesis rapid uninterrupted. oogenesis arrested at specific stages.
outline steps of fertilisation
sperm penetrates follicle cell and zona pellucida.
binding of sperm to egg surface (acrosomal reaction/ enzyme digestion)
cortical reaction (stops multiple sperm fusing to one egg)
formation of a diploid zygote from 2 haploid cells.
most significant cause of human infertility
defective sperm
what is ICSI
ICSI is intracytoplasmic sperm injection where a single spem is injected directly into mature egg.
Where do all tissues originate from
the inner cell mass of the blastocyst.
what is the blastocyst
cavity of fluid and inner cell mass produced in the cleavage stage of development. the outer layer of the blastocyst is the trophoblast which forms part of the placenta. it attaches to the uterine wall where cells proliferate out into wall.
outline the epiblast and hypoblast
the inner cell mass forms a flat disk with the epiblast, top layer and hypoblast, bottom layer. When these are formed an amniotic cavity also forms
outline gastrulation
rapid cell movement and proliferation where the epiblast gives rise to 3 germ layers endoderm ectoderm and mesoderm from which all tissues derive.
What are stem cells
undifferentiated cells that can self renew via mitosis and differentiate into 1 or more specialised cells.
what is potency
a measure of ability to differentiate into a range cells.
totipotent: produce an entire organism
pluripotent: gives rise to cell derivates of all 3 germ layers
multipotent: gives rise to multiple cell types but does not normally generate cells from all three germ layers.
what are iPS
induced pluripotent stem cells are stem cells that are made from somatic cells by reprogramming them with different added factors to change their DNA and create a stem cell.
spermatogonium, spermatocyte, spermatid
spermatogonium: diploid precursor cell that gives rise to sperm
spermatocyte: primary and secondary cells formed from spermatogonium
spermatid: early sperm cell
spermatoozon: mature sperm cell
