Human Genetics test 1 Flashcards
when will you see a chromatid?
in the DNA duplication phase during the S phase of the cell cycle back in interphase (mitosis or meiosis
def of centromere?
single connecting piece of protein that holds the two chromatids together
what is the chromosome compliment in humans?
diploidy (23 pairs 46 chromosomes)
def of autosomes?
22 homologous pairs behaved indepently from eachother and are not directly related to the sex of the individual
what are the three basic ways to identify chromosomes?
size, centromere location, staining and banding
def of metacentric?
centroemre is n the middle
def of submetacentric?
little off of the center
def of acrocentric?
near the end of the tip
def of chromosome satellites?
small masses of the chromosomes that are bulged that contain DNA for ribosomal synthesis
what is the paris conference system?
after various chemical staining treatments you can read the chromosomes as a bar code
what is the International System of Human Chromosome Nomenclature?
the thing that we use today
what is the P arm?
the short arm
what is the q arm?
long arm
how is a karyotype conventionally abbreviated?
listing the total number of chromosomes, followed by sex chromosomes, followed by any derangement in the chromosomes
what does the modern way of karyotyping helpful with?
revealing major and minor deletions, duplications, larger rearrangements and translocations
def of euploidy
having a complete set of chromosomes
def of haploidy
one complete set
def of diploidy?
2 complete sets
def of aneuploidy?
where one chromosome is missing or an extra one is present
def of monosomy?
a chromosome is missing from a homologous pair
how many total chromosomes in monosomy?
45
def of trisomy?
a chromosome is added to a homologous pair
how is trisomy described?
2N+1
how many total chromosomes in trisomy?
47
what is the facies of down syndrome?
oblique palpebral fissures, epicanthic folds
what are the neurological signs of down syndrome?
hypotonia, mental retardation
what percentage of mental retardation is from down syndrome?
1/3rd
how can you screen for down syndrome?
amniocentesis, chorionic-villus sampling, ULTRASOUND OF NUCHAL AREA TRANSLUCENCY
what is the recurrent risk of women under 40?
about 1 percent
how are aneuploidy’s get made?
produced from non disjunction durning anaphase (one or two)
def of deletion?
partial monosomy wherein a piece of a chromosme is deleted
what is prader-willi and angelman syndrome?
disorders involving a spontaneous deletion of 15q11 to 15q13
prader-willi is a defect of paternal or maternal homolouge?
paternal
Angelman syndrome is a defect of a paternal or maternal homolouge?
maternal
def of imprinting?
a phenomenon whereby inherited chromosomes from one parent are modified such that the genes at that location are not properly expressed
what is cri du chat syndrome?
a rare disorder involving a spontaneous deletion from 5p14 to 5p15
what are the symptoms cri du chat?
cats cry syndrome, cat like cry during infancy
def of duplication?
a piece of a chromosome is duplicated
what do significant duplications revealed as?
added or altered bands (smaller difficult to detect)
what is pallister killian syndrome? (fyi)
duplication on 12
Inversion def?
wherein a piece of chromosome is flipped around or inverted
where do you see significant inversions?
as reversed bands and the centromere may be in different spot
translocation def?
two chromosomes break and exchange places
what percent of trisomy 21 are translocation?
5.00%
what are the potential offspring of translocation down syndrome
normal, monosomy 21 (nonviable), translocation down sydrome, translocation down sydrome “carrier” (normal)
what is chronic myelogenous leukemia?
rare cancer though a common form of leukemia with an exchange b/t chromosome 9 and 12 t(9:22)
what is the “philadelphia chromosome?”
t(9:22) which is seen as a stubby chrom 22
what is the ratio of live births with a chromosome deformity?
1 in 200
what percentage of recognizable pregnancies abort?
15.00%
what percentage of miscarriages conceptuses have a normal karyotype?
about 1/2 of 15% of recognizable pregnancies
how common are chromosomal defects in any type of pregnancy (miscarrage or not)
01/01/00
what percentage of livebirths are chromosomally abnormal?
0.6% (50:8,500)
what is the incidence of a chromosomal disease a function of?
function of the conceptus production rate AND the likelihood of in utero survival
what does repeated miscarriages suggestive of?
a chromosomal defect in either one or both rents
what are the roles of meiosis?
formation of gametes, reduction of chromosome number, random assortment, and crossing over
def of random assortment?
jumbling of maternal and paternal chromos
def of crossing over?
jumbling of maternal and paternal chromosomal segments
what is meiosis 1?
separation of homologous pairs
what is meiosis 2?
separation of chromatids
what is pre-meiotic interphase?
only chromaTIN visable in nucleus as DNA double
what is prophase 1?
chromoSOMES appear and cont. condensing
what is metaphase 1?
HOMOLOGOUS PAIRS of chromosomes line-up on an equatorial plane and are attached to a spindle apparatus
what is anaphase?
separationof homologous pairs
def of disjunction?
separation of homologous pairs
what is telophase?
reconstruction of the nuclei and division of the cytoplasm
what is prophase 2?
recoiling of chromosomes to managable size
what is metaphase 2?
single chromo line up on equatorial plane and attach to a new spindle apparatus
what is anaphase 2?
separation of chromaTIDS
def of telophase 2?
final reconstruction period: chromosomes uncoil to chromaTIN
what is post-meiotic interphase?
two haploid daughter cells created
how many cells will you see at the end of meiosis?
4
do each of the new cells at the end of meiosis have the same amount of DNA compared to the start?
yes
def of gene?
1) a nucleotide coding for a specific protein. 2) the smallest unit of biological function
what is the DNA organization?
Nucleotides>codons>domains>genes>gene clusters> Chromosome bands> chromosome arms> chromosomes> karyotype
how many genes are in the human genome?
25000
how many different base pairs are in the human genome?
3 billion and 99% are non-coding
def polymorphisms
significant allelic variation
what does it mean for a gene to be conserved?
the critical genes for metabolic function donﾒt vary too much
def mutant allele
some variant, does not have to be bad
what are point mutations?
the most common mutation where a single base pair changes. Which may or may not cause changes in the final polypeptide
def of genotype
the genetic constitution of an individual organism
def of phenotype?
a set of observable characteristics of an individual from the interaction of its genotype with the enviroment
def of incomplete dominance?
niether allelic form in a heterozygote is fully expressed, producing intermediate phenotypes beyond the basic combos of multiple heterozygous forms
def of mutation?
any change in genetic material
what is the class of disease is sickle cell anemia part of?
hemoglobinopathies
what causes sickle cell anemia
single base pair substitution in the beta-globulin gene on chromosome 11
what are the two broad sources of mutations?
radiation and chemicals
what are the things that cause radation mutations?
cosmic rays, solar energy, radioactive decay and x-rays
what re the things that cause chemical mutations?
(AKA mutagens) polycyclic aromatic hydrocarbons,, and oxidative agents
what is a tautomeric shift?
the nucleotide thiymine can shift into its -enol form where it can then pair with guanine not adenine
what did hermann muller do?
in 1927 showed that x-rays are mutagenic
what did charlotte auerback do?
in 1941 showed that mustard gays is mutagenic
def of loss-of-function mutation?
loss of the genes function;later seen to be recessive
def of gain-of-function mutation?
gene gains a function; later seen to be dominant
def of dominant negative mutations?
acts as a antagonistically to othe normal state; later seen to be dominant or co-dominant
def of lethal mutations
worst possible dna change.. Often in urero
def of genetic load?
a somatic cell accumulates about 30 new mutations in a lifetime
what is gene expression “about”?
health and disease
def of epigenetics?
trying to understand the gene expression which will show what it means to have a genetic disease
def structural genes?
code for components in or out of the cell
what happens if a structural gene fails?
dominant negative mutations
def of metabolic genes?
code ofr metabolic components that control reactions
what happens if a metabolic gene fails?
usually recessive mutation
what is harrtnup disease?
defective tryptophan transport across membrane (Ta)
in hartnup disease is the diseased gene dominant or recessive?
homozygous recessive= hh
what is the clinical feature of hartnup disease?
niacin deficiency
what is galactosemia?
disorder of defective carbohydrate metabolism inside cell (Ebc) which leads to an accumulation of galactose in gut
in galactosemia is the diseased gene dominant or recessive?
homozygous recessive= hh
clinical features of galactosemia?
gi problems, cataracts, cirrhosis
what is albinism?
a disorder of amino acid metabolism (Eab) which results in a defiency of melanin in regularly pigmented tissues
in albanism is the diseased gene dominant or recessive?
homozygous recessive= hh
what is PKU?
a disorder of amino acid metabolism (Eab and F and G) which results in an accumlation of phenyalanine in the body because it can not be changed to tyrosine by phenylalanine hydroxylase
in PKU is the diseased gene dominant or recessive?
homozygous recessive= hh
what are the symptoms of PKU?
severe mental retardation, hypo-pigmentation, and unusual odor
what is Lesch-Nyhan syndrome?
disorder of purine metabolism inside of the cell which results in deficiency of adenosine and the accumulation of uric acid
what sex will you see lesch-nyhan?
since itﾒs on the x chromosome and the mutant allele is recessive you only see it in males
wgat are the symptoms of lesch nyhan?
mental retardation, HYPERURICEMIA
def of gradual onset of metabolism?
metabolite needs time to accumulate to cause problem
def of unusual dietary response to metabolism?
to a metabolite that cannot be metabolized
what is the Iac operon in prokaryotes?
a promoter sequence sits next to a series of genes that control the production of the enzymatic machinery to digest lactose
what is the homeobox (HOX)?
highly conserved, gene grouping that code for transcription factor that regulates the cascade expression
where will you see HOX?
chromosomes 2,7,12,17
what is the function of HOX?
control patterning of the body axis and the resultant development of body organs
def of variable expressivity?
variable presentation of phenotype and remember that enviroment may play a role in the phenotype
def of penetrance
expression/non-expression of a dominant gene
when a disease has less than 100% penetrance what do you do?
take an expected probability and multiply it by the percent penetrance
def of pleiotropy?
where one gene effects mulitple traits (in cats single gene does white fur, blue eyes and blindness)
how is monosomy described?
2N-1
