Intro To Genetics Flashcards
What is the structure of the nucleosome?
It consists of Octomer made of pairs of H2A, H2B, H3 and H4
Where is the location of the H1
On the surface of the nucleosome
What is the chromosome structure?
Centromere in the mid region divides a chromosome in a short arm (p) and a long arm (q)
What are the stages of the cell cycle?
Interphase
Mitosis
What are the stages of interphase?
G1: Synthesis of proteins, checking for DNA damage
S:DNA replication
G2: checking for DNA damage and duplication of centrioles
What are the stages of mitosis
Prophase
Metaphase
Anaphase
Telophase
What are the characteristics of the prophase?
Threadlike chromosomes where sister chromosomes are joined by cohesins
Kinetochore protein serves as an attachment to microtubules
Centrosomes migrate to opposite poles
Nuclear envelope disintegrates
What are the characteristics of the metaphase?
Chromosomes condense and attach to mitotic spindle
Chromosomes align at equatorial plane
What are the characteristics of anaphase?
Sister chromatids separate and move toward opposite poles
What are the characteristics of the telophase?
2 Sets of chromosomes are at the spindle poles
What are the stages of prophase I of meiosis?
Leptotene Zygotene Pachytene Diplotene Diakinesis
What are the characteristics of Leptotene?
Chromatin condenses
Sister chromatids condense and connect
Pairing of homologous chromosomes initiated
What are the characteristics of Zygotene?
Synapsis begins and continue till pachytene
Synaptonemal complex is formed by transverse filaments
What are the characteristics of Pachytene?
Synapsis is complete
Crossing over occurs
what are the characteristics of Diplotene?
Synaptonemal complex dissolves
Sister chromatids separate except in chiasmata
What are the characteristics of Diakinesis?
Chromosomes shortens
Nucleolus and nuclear envelope disintegrates
What are the characteristics of metaphase I?
Paired chromosomes aligned at the equatorial plate
Homologous chromosomes held together by chiasmata
What are the characteristics of anaphase I and telophase I?
Similar to mitosis except centromeres do not split
Sister chromatids held together by cohesion and centromere
What are the characteristics of gametogenesis?
Consists of meiosis and cytodifferenciation
Primordial germ cells formed in the epiblast during the second week
Move through the primitive streak to yolk sac
PGCs migrate to gonads from yolk sac during 4th week
Arrive at the gonads at the 5th week
What are the characteristics of Oogenesis?
Before birth PGCs differentiate to oogonia
OOgonium goes through mitotic division to give primary oocyte
By the time of birth primary oocytes have started prophase of meiosis I and rest at diplotene stage
At puberty primary oocyte resume and give secondary oocyte.
Secondary oocyte goes through meiosis II and stop at metaphase
What are the characteristics of the Spermatogenesis?
PGCS give rise to spermatogonial stem cells supported by Sertoli cells
Spermatogonial cells give type A and type B spermatogonia
Type B becomes resting primary spermatocyte
Primary spermatocyte becomes secondary spermatocyte and spermatic after 2 meiotic divisions
At puberty spermatic goes through spermiogenesis
Acrosome form, nucleus condense and shed cytoplasm
What are the types of chromosomal abnormalities?
Numerical-Euploid(multiples of n) and aneuploid(not euploid)
Structural-microdeletion
Nondisjunction (trisomy, monosomy)
Translocations
What are the characteristics of trisomy 21 (down syndrome)?
Growth retardation
Intellectual disability
Craniofacial abnormalities (upward slanted eyes)
Epicanthal folds
Cardiac defects
Increased chances of leukemia, infections and Alzheimer’s
What are the characteristics of Trisomy 18?
Intellectual disability Congenital heart defects Low set ears Flexion of fingers and hands Micrognathia(undersize jaw)
