week 1: human genetics, genetic disorders Flashcards
what is a genome?
The genome is all the DNA in the cell.
All the DNA on all the chromosomes.
what are the three genomes a eukaryotic cell can have?
- nuclear genome
- Mitochondrial genome
- plastid genome
What is genomics?
it is the study of genomes including large chromosomal segments containing many genes.
how many chromosomes does a human somatic cell contain?
22 autosomal pairs and one sex chromosome (total of 23)
how does alternative splicing effect polypeptide production?
human genomes can produce more than one polypeptide per gene because of alternative splicing of RNA transcripts.
what method was used during the human genome project?
The genome was completed using sequencing machines and the dideoxy chain termination method
what is the structure of the human genome?
contains regulatory sequences, exons and introns
what contributes to non coding DNA
- introns
- regulatory elements of genes
- multiple copies of genes, including pseudogenes
- intergenic sequences
- interspersed repeats
what are pseudogenes?
former genes that have mutated and are no longer functional
what are transposable elements?
move from one site to another in a cell’s DNA
eukaryotic transposable elements have two types; what are transposons and retrotransposons?
transposons move by means of a DNA intermediate and require a transposase enzyme.
Retrotransposons move by means of an RNA intermediate using a reverse transcriptase.
what are Alu elements?
they are transcribed into RNA molecules; some are thought to help regulate gene expression.
what is a series of repeating units of 2 to 5 nucleotides called?
Short Tandem Repeat (STR)
________ are variations in the number of repeats of specific DNA sequences
STR’s
how will a mutation affect a genome?
a single base may mutate or a large segment of a chromosome
what type of mutation is passed onto offspring somatic (body) cell or germ-line mutations.
germline mutation are passes on and somatic mutations are not passed on and usually give rise to cancer or other diseases.
what is a mutagen?
a natural or human made agent (physical or chemical) which can alter the structure or sequence of DNA.
name 4 types of chemical mutagens
- base analogs (bromouracil)
- chemicals which alter structure and pairing of bases (nitrous acid)
- intercalating agents (ethidium bromide)
- DNA structure altering (peroxides)
name 2 types of radiation mutagens
EM spectrum and ionizing radiation
what is a point/substitution mutation?
a base change in the DNA.
can be silent missense or nonsense.
describe insertion or deletion mutations
addition or removal of one or more nucleotides.
introduces a frameshift mutation.
describe an allele (3 things)
-an allele is a variant from a gene
-humans are diploid organisms as they have two alleles at each genetic locus
-one allele is inherited from each parent.
difference between dominant and recessive alleles
a recessive allele only shows if there are two present
a dominant allele always shows
what types of gene disorders can be inherited?
autosomal recessive and sex linked
how is sickle cell anemia cause and what are the symptoms?
caused my a missense mutation
-red blood cell is an abnormal crescent shape.
-hemoglobin is abnormally shaped.
-forms clumps and does not move easily through blood vessels.
cystic fibrosis:
is it a recessive or dominant disorder?
what are the symptoms?
autosomal recessive disorder
-thick mucus in lungs
-constant lung infections and impaired digestion
it affects 1 in 2500 white births
what causes cystic fibrosis?
deletion mutation which causes there to be an amino acid missing in the protein and it cant fold correctly.
is PKU recessive or dominant?
it is an autosomal recessive disorder.
what causes PKU?
and what are the symptoms?
how is it regulated?
it is the deficiency of an enzyme that is required for the proper metabolism of amino acid phenylalanine.
loss of the PAH enzyme results in mental retardation, organ damage, unusual posture and ca compromise pregnancy
regulated through strict diet with no dairy (low in phenylalanine and high in tyrosine
describe Huntington’s disease/chorea
(3 points)
it is an autosomal DOMINANT disorder
it is an inherited degenerative brain disorder eventually resulting in loss of mental and physical control
chorea means “dance like movements” and refers to the uncontrollable movements.
what are the 4 types of chromosomal mutations?
translocation
inversion
duplication
deletion
describe translocation chromosome mutation
segments of different chromosomes are exchanged
an example is Burkitt’s Lymphoma
(cancer of the lymph nodes, in children)
describe inversion chromosome mutation
a segment of the chromosome is flipped
(inverted)
an example is Four-Ring Syndrome
(cleft pallate, club feet, testes don’t descend)
describe duplication chromosomal mutation
a segment of one chromosome moves to the same location of a homologous chromosome
an example is Charcot–Marie–Tooth disease
(high arched foot, claw feet, confined to a
wheelchair)
describe a deletion chromosomal mutation
a segment of a chromosome is removed
one example is cri du chat - deletion of part of chromosome 5.
what is nondisjunction?
chromatids fail to separate during meiosis.
what is an aneuploidy
a gamete that contains an abnormal number of chromosomes.
examples of diseases that occur with nondisjunction
- down syndrome - caused by having one extra 21st chromosome
- Kleifelter’s syndrome - occurs when a male has one extra x chromosome.
- occurs when females have one less x chromosome.
