Chromosomes
vehicles carrying information from one (cell) generation to the next
chromosomes are complex structures of...
dna, histone proteins, and non-histone proteins
chromosome abnormalities are common causes of?
infertility and recurrent miscarriage
Chromosome cause __ % of __ trimester miscarriages
50%, first
chromosome abnormalities result in multiple congenital anomalies in ~__ % of newborns
0.50%
chromosome abnormalities are ___ and parents are/aren't normal
spontaneous, are
what kind of cells do chromosome abnormalities accumulate in?
cancer cells
chrosome abnormalities consist in changes in chromosomes __ or __
number or structure
Types of numerical changes in numerical chromosomal abnormalities
Polyploidy and Aneuploidy
Polyploidy
-Chromosomal abnormality (numerical) -affects 1% of conceptuses -changes in the number of all chromosomes EQUALLY -e.g. triploidy (3 entire genome copies), tetraploidy (4 entire genome copies-always lethal, after a few number of cell divisions
Aneuploidy
-Chromosomal abnormality (numerical)-Affects ~1 in 300 newborns-changes in the number of one or multiple chromosomes UNEQUALLY-e.g. monosomy, trisomy, tetrasomy (1,3, or 4 copies of a single chromsome)
Numerical abnormalities affect what?
the total number of chromosomes an individual carries
structural abnormalities affect what?
they do NOT affect the total number of chromosomes but alter the content of individual chromosomes
Most numerical abnormalities of SOMATIC chromosomes are incompatible with human life, which abnormalities are the exception?
Trisomies 13, 18, and 21Trisomy 13 and Trisomy 18 do not make it to adult hoodTrisomy 21 -down syndrome is the only that makes it to adult hood
Numerical abnormalities of SEX chromosomes are more likely to result in viability, provide one example
Turner's syndrome
Triploids arise before, during, or after fertilization?
They arise by fertilization of a single egg by two sperm. or a diploid egg or sperm. Abort spontaneously, very rare to survive to term
Tetraploidy arises before, during, or after fertilization?
results from the failure of the first mitotic division AFTER fertilization, and is compatible with development.
What are two types of structural abnormalities?
Balanced abnormality and unbalanced abnormality
Balanced abnormality
#NAME?
Unbalanced Abnormality
-Structural Abnormality-Deletion and Duplication-Gain or loss of genetic material, usually major clinical consequences. The duplication results in a gain of genetic material- partial trisomy. With the deletion- partial monosomyFull monosomy is usually lethal except for trisomy 13,18, and 21
Aneuploidy
Numerical abnormalityloss of genetic material and gain of genetic materialloss of genetic material results in monosomy and a gain of genetic material results in a trisomy
Chromosomes condense during which phase?
Prophase
As chromosomes condense during prophase, what holds the length of the chromatids together?
cohesin
During which phase is cohesin removed but still remained at the centeromere?
metaphase
What enzyme does protelytically degrade cohesin at the centromeres allowing the separation of chromatids?
Separase
Druing meiosis the gametes are/are not genetically identical
They are genetically identical
During meiosis, the gamates may contain what? what may occur
potential exam questionmay contain either maternal or paternal chromsomes recombination
which phase during the cell cycle does crossing over occur?
prophase I
mendels 3rd law
maternal and paternal homologs of different chromosomes segragate independently in meiosis i 2^23 or 8.4 million possible combinations -first level of individual genetic variation
what is the second level of genetic diversity
recombination
When does spermatogenesis commence in males?
puberty
when does oogenesis commence in females?
early embryonic life
duration of gametogenesis in males vs. females
male: 60-65 daysfemale: 10-50 years
number of mitoses in gamete formatino in male vs females?
male: 30-500female: 20-30
gamete production per meiosis in males vs females?
male: 4 spermatidsfemale: 1 ovum +3 polar bodies
gamete production per ejaculate in males vs females?
males: 100-200 millionfemales: 1 ovum per menstural cycle
cytogenetics
study of human chromosomes, their structure, inheritance, and abnormalities
karyotype
an individual chromosome constitution also describes a display of a person's chromosomes
When preparing a karyotype, what prevents spindle formations so cells arrest in metaphase
colchicine
what are acrocentric chromosomes in humans?
13, 14, 15, and 21
what are karyotypes stained with?
gimesa
what gene is mutated in cystic fibrosis
CFTR
Read this structural abnormality:46, XY, del (22)
-male with 46 chromosomes and a deletion on chromosome 22 with a break point at band q21(recall-q is the long)
Read this structural abnormality:46, XX, inv(7), (p11,q22)
female with 46 chromosomes and an inversion on chromosomes 7 with breakpoints at bands p11 and q22
Read this structural abnormality:47, XX+21
Female with an extra copy of chromosome 21, trisomy 21, or down sydnrome
Read this structural abnormality:46,XX, t(1;6)(p23;q21)
female with 46 chromosomes and a translocation between chromosomes 1 and 6with breakpoints at band p23 on the short arm of chromosome 1 and a band q21 on the long arm of chromosome 6