Division and Chromosomal Heredity Flashcards
what are the different morphological types of chromosomes
metacentric-equal length arms
submetacentric-p arm shorter
acrocentric-no p arm
differences between homologous chromosomes and sister chromatids
Homologous-similar NOT IDENTICAL. carry different versions of the same gene
Sister-genetically identical
how many pairs of chromosomes are found in a typical human somatic cell
23 pairs(46 chromosomes)
prime difference between mitosis and meiosis
mitosis produces diploid cells 2 genetically identical (diploid) daughter cells
meiosis produces 4 genetically different haploid cells for sexual reproduction
T/F between interphase and mitosis cells can enter G0 stage in which they are quiescent
True
T/F DNA synthesis occurs during S phase of interphase stage
TRUE. DNA is replicated
T/F the interphase is characterized by absence of visible chromosomes
TRUE
T/F transitions from one interphase stage to the other are controlled by cell cycle checkpoints
TRUE
what is the role of chromosomes in cell division
allow DNA to be replicated accurately
what is a karyotype? when is the best time to obtain one during mitosis?
image of a complete set of chromosomes in an organism taken during metaphase
stages of mitosis and brief description
Prophase-nuclear membrane breakdown
Prometaphase- chromosomes begin to condense, formation of spindles
Metaphase-full chromosome condensation, spindles attach
Anaphase-separation of sister Chromatids
Telophase-formation of 2 new nuclear membranes
if 2n=6 how many DNA molecules and chromosomes are there for each cell in:
G1
G2
mitotic metaphase
mitotic anaphase
G1: 6 chromosomes, 6 DNA molecules
G2: 6 chromosomes, 12 DNA molecules
mitotic metaphase: 6 chromosomes, 12 DNA molecules
mitotic anaphase: 12 chromosomes, 12 DNA molecules
what is the effect of colchicine on the cell cycle
causes damage to the spindle and arrests mitosis(at metaphase)
T/F at completion of metaphase, the chromosomes align in metaphase plate with spindles attached to TELOMERES
FALSE. They attach at the kinetochore
what is karyokinesis? what phase does it occur
formation of 2 new nuclear membranes. occurs during telophase
what is cytokinesis? what phase does it occur
formation of 2 new cell membranes, occurs during telophase
stages of meiotic division and brief description
prophase I(5 stages)
metaphase I-tetrads orient on metaphase plate
Anaphase I-disjunction (separation of homologs)
Telophase I-much shorter than mitotic phase
Prophase II-telophase II-similar to mitosis
explain monad, dyad, and tetrad, and how many DNA molecules and strands in each
Monad-1 molecule, 2 strands
Dyad-2 molecules, 4 strands
tetrad-4 molecules, 8 strands
what are chiasmata and when do they occur?
site of recombination, occurs in prophase I (pachynema)
what is crossing over? what is its biological importance?
homologs exchange genetic material
leads to genetic variation
T/F in spermatogenesis, spermatogonia undergo first meiotic division to produce primary spermatocytes
TRUE
what are recombination hotspots? what is an example?
they are short regions all over genome for recombination
-major histocompatibility complex
-pseudoautosomal region in males
what are recombination coldspots? what are examples?
on centromeres
T/F secondary spermatocytes undergo meiosis II to produce haploid spermatids
TRUE, however sperm cells become haploid after meiosis I
T/F in oogenesis primary oocytes are diploid as well as the secondary oocytes
TRUE, they become haploid after second meiotic division
T/F polar bodies are the result of equal cytoplasm division during meiosis I
FALSE. cytoplasm division is unequal
what is the dictyate stage?
oogenesis arresting at diplonema during meiosis I
unique features of meiosis in female mammals
all mammalian females are mosaics for maternal and paternal X-linked alleles
what kind of trait is milk production? in mammals why do only females have milk production?
it is a sex limited trait. hormones in females activate mammary glands
sex-limited vs sex influenced
sex-limited: expression of specific phenotype is absolutely limited to one sex
sex-influenced: sex influences phenotype, but it is not limited to one sex
examples of sex limited traits
breast development
beard growth
examples of sex influenced traits
pattern baldness
what mechanism balances expression levels of genes found on X chromosomes between genders
Barr bodies/dosage compensation
what are barr bodies
heterochromic X-chromosome, histones are deacylated, DNA is methylated
which group of genes escape X inactivation
PAR
X-Y gemetologs
which features of X inactivation causes large patches of orange and black color to appear in tortoiseshell cats
random X inactivation
what is the role of the XIST mechanism in the X inactivation process
X-inactivation specific transcript, produces large RNA molecule to “paint” the chromosome to be inactive
what kind of gene is XIST
non coding RNA
what is the importance of the SRY gene
produces transcription factor needed for male-specific gene expression
2 main sex chromosome systems in nature, how do they differ?
X/Y system, based on presence/absence or SRY
Z/W system, used in birds and reptiles females are Z/W, and males are ZZ
explain drosophila sex determination A:X ratio
sex is determined by ratio of X chromosomes to autosomes(A)
females: 1:1 (AA XX)
males- 2:1 (AA X)
5 stages of Prophase I
leptonema
zygonema
pachynema
diplonema
diakinesis
leptonema
homologs find each other
zygonema
start of homolog pairing
pachynema
homolog pairing complete, formation of tetrads, start of crossing over
Diplonema
non sister chromatids start to separate
diakinesis
nuclear envelope dissolve so cell can enter metaphase
