2. Genes and Genetic Diseases Flashcards
insertion or deletion of 1 or more base pairs
frameshift mutation
RNA directs synthesis of a polypeptide at a ribosome
translation
RNA is synthesized from DNA template and form messenger RNA (mRNA)
transcription
silent, missence, and nonsense are all what type of genetic mutation
base pair substitution
What is seen in Down syndrome?
intellectual disability, distinctive facial features, and increased risk of leukemia
only 1 gene needed for expression; genders equal
autosomal dominant
cells w/ compete extra sets of chromosomes
polyploidy (usually spontaneous aborted or stillborn)
exchange of material between 2 non-homologous chromosomes
reciprocal translocation
mutation -> new codon -> new AA
missense mutation
On what chromosomes do Robersonian translocations occur?
13, 14, 15, 21, and 22
What AD disease is known for its delayed age of onset (about 40 y/o)?
Huntington’s disease
harmful agent that increases risk of chromosomal breakage
clastogen (ionizing radiation, viral infection)
long arms of 2 non-homologous chromosomes combine at the centromere to form a single chromosome and the short arms are usually lost
Robertsonian translocation
List 3 examples of autosomal dominant disorders
Huntington’s disease, Von Willebrand’s disease, and Marfan’s syndrome
genes position along a chromosome
locus
Chromosomes and pairs of gametes
23 chromosomes as singles (haploid)
Example of expressivity
neurofibromatosis
Fragile X Syndrome
gap on long arm of X chromosome
certain number of factors/genes must be affected before phenotype is expressed
threshold of liability
any agent known to increase frequency of mutation
mutagen
Turner Syndrome
Monosomy X
What role does the ribosome play in forming a polypeptide?
provides an enzyme that catalyzes the formation of covalent peptide bonds between adjacent AA -> growing polypeptide chain
What chromosome is cystic fibrosis linked to?
chromosome 7
Cri-du-chat syndrome
Chromosome 5 - deletion of short arm
What is seen in Klinefelter syndrome?
breast development, small testicles, typically sterile and some intellectual impairment
Klinefelter Syndrome
XXY condition
cells w/ a multiple of the normal number of chromosomes
euploid cells
describe the chromosomes in triploidy and tetraploidy cells
- triploidy = 3 complete sets of chromosomes - tetraploidy = 4 complete sets of chromosomes
Patau syndrome
trisomy 13
Edward’s syndrome
trisomy 18
aneuploidy is a result of what?
nondisjunction - homologous chromosomes or sister chromatids fail to separate during mitosis or meiosis
Name 4 types of abnormalities in chromosome structure
- deletion - duplication - inversion - translocation
List 3 examples of AR diseases
cystic fibrosis, sickle cell anemia, and albinism
range of phenotypes that vary between patients and specific genotype
expressivity
what is the recurrence of autosomal dominant
50%
traits in which variations are caused by combined effect of multiple genes (polygenic)
multifactorial inhertence
different forms of a gene
alleles
List 3 examples of X-linked inheritance
color blindness, Duchenne muscular dystrophy, and hemophilia A
RNA sequences that are spliced out are called ___ and sequences that become mRNA to code for proteins are called ___
introns; exons
Newborns w/ trisomy of what chromosomes can survive?
trisomy 13, 18, 21, or X
Down Syndrome
Trisomy 21
mutations located on the X chromosome; females usually carriers; males affected
X-linked Inheritance
name 2 types of aneuploidy cells and which type is worse
monosomy and trisomy; monosomy is worse due to the lack of genetic material
What molecule includes the site where the AA attaches during translation?
the tRNA
What is the recurrence of autosomal recessive?
50% carrier, 25% normal; 25% affected
Chromosomes and pairs of somatic cells
46 chromosomes in 23 pairs (diploid)
a cell that does not contain a multiple of 23 chromosomes (missing or additional individual chromosomes)
aneuploidy
What is expressivity influenced by?
environment, genes at other loci and mutations at different points on loci
What is a common example of incomplete penetrance
retinoblastoma - about 90% who carry the gene will get the disease (90% penetrance)
What is seen in cri-du-chat syndrome?
low birth weight, severe intellectual disability, microcephaly, heart defects, and characteristic high pitched cry
% of individuals w/ a genotype who also exhibit the expected phenotype
penetrance
a locus that has 2 or more alleles that each occur with an appreciable frequency in a population
polymorphic
mutation -> new codon -> same AA
silent mutation
mutation -> new codon -> stop codon
nonsense mutation
only an extra portion of a chromosome is present in each cell
partial trisomy
What is seen in Turner syndrome?
short stature, neck webbing, spaced nipples, usually sterile, but no intellectual disability
individuals w/ disease-causing genotype but not the phenotype
incomplete penetrance
What is seen in Fragile X syndrome?
more common in males; causes intellectual disability (2nd most common under Down syndrome)
2 copies of the genes needed to influence the phenotype; genders equal
autosomal recessive
