Genetics week 1 Flashcards
Gene
segment of DNA that encodes a specific thing (amino acid, regulational RNA etc.)
Allele
alternative forms of a gene (DNA at a specific locus) that differ in sequence
Locus
a physical region of a chromosome; often used to refer to segment of DNA that contains a specific gene
Genetics
science of genes/DNA
Homologous chromosomes
chromosomes that pair during meiosis one derived from each parent. Although not identical, normally only a few base pair differences in each gene
sister chromatids
2 identical duplicated chromosomes joined by a single centromere
Ploidy
the number of copies of the c-some
Haploid
one copy of each c-some
Diploid
2 copies of each c-somes
Aneuploid
any number of c-some that is not an exact multiple of the haploid number
Monosomy/Trisomy
result of nondisjunction during meiosis or mitosis resulting in the absence of a single c-some or the presence of an extra c-some
Maternal serum ARP screening/Quad test
this is a screening test, it does not diagnose a problem; it only signals that further testing should be done
Measures serum alpha-fetoprotein
somatic cell
other than those of the gamete-forming germ line
Most somatic cells in humans are diploid
germ line cells
cells responsible for the production of gametes
gametes
haploid germ cells (sperm and ova)
zygotes
two gametes fuse (fertilization)
Mitosis
Meiosis
Mitosis is the general propagation of cells, end up with diploid cells
Meiosis utilizes another propagation of division, end up with haploid cells
crossing over
exchange of genetic material between homologous c-somes that results in recombinant c-some
synapsis
binding of the 2 homologous c-somes
spermatogenesis
mitosis occurs throughout life. At puberty meiotic division is induced with millions of sperm being produced
Continues throughout life
Oogenesis
all mitosis occurs in development
At birth, all precursor cells arrested in prophase division 1. At puberty, 1 oocyte matures (finished meiosis) and is released per cycle
Ends at menopause
Advanced paternal age is associated with what kind of mutation?
replication errors, single BP mutation
Advanced maternal age is associated with what of mutation?
trisomies and non disjunction
Promoter sequences
controls levels of mRNA expression which controls levels of protein expressed
coding sequences
exons, specify the sequence of amino acids in proteins
Intervening sequences
introns, interrupt coding sequences. mRNA splicing
Structural regions
Untranscribed regions and 5’-3’ untranslated regions in mRNA
core basal promoter
determines the transcription star site, and whether transcription occurs
ex. TATA box
Regulatory Domains (elements)
They determine when where and how much transcription occurs
ex. enhancers
Conservative missense mutation
Point mutation that alters one amino acid to another amino acid with similar properties
ex. Ile -> Leu
Non-conservative missense mutation
Point mutation that alters one amino acid to another amino acid w/ different properties
ex. Ser -> Phe
Nonsense mutation
point mutation that results in premature stop codon
results in truncated protein
Promotor mutations
effect levels of protein expression by effecting levels of RNA expression
Haplosufficiency
one normal allele is enough to mask the effects of the mutant
recessive disorder
Haploinsufficiency
one normal allele is NOT enough to mask the effects of the mutant allele (dosage sensitivity)
Dominant disorders
Gain of Function mutation
novel protein product or over-expression/mis-expression (ex. in wrong tissue) of a normal protein
ex.dominant disorders like Trisomies
Dominant negative mutation
mutant protein inhibits the activity of the normal protein
ex. multimeric proteins
Principle of Segregation
genes occur in pairs in individuals, one copy inherited from each parent; only one of each is transmitted to the offspring in the next generation
Principle of Independent Assortment
alleles of different genes are transmitted independently
Not true for genes that are located close together (linkage)
genotype
the genetic constitution of an individual, or the two alleles inherited at a specific genetic locus
phenotype
observable consequence of a given genotype and environment
co-dominant
the phenotype of the heterozygote is distinguishable from either of the homozygotes
Risk of occurence
probability that a couple will have an affected child.
Depends on population frequencies of the disorder and the rate of spontaneous mutation
Risk of recurrence
the probability that a genetic disorder that has occurred in a family will recur in another member in the same or in future generations.
Depends on mode of inheritance
gene frequency
percentage of a specific allele of a gene in a population
genotype frequency
proportion of a population w/ a specific genotype (combo of 2 alleles)
