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