Genetics Flashcards
(19 cards)
Gene
sections of DNA, contained within chromosomes
Chromosomes
Chromosomes: a complicated strand of DNA and protein, made of 2 chromatids joined by a centromere. Normally each human cell contains 46 chromosomes (23 pairs)
DNA
deoxyribonucleic acid, part of the double helix chromosome
Allele
Genes that occupy corresponding loci (locations on the chromosome) that both determine the same characteristic
Sex chromosomes
XX in females, and XY in males
Autosomes
the 22 pairs of chromosomes that determine physical characteristics other than the gender
Phenotype
when a genotype (type of gene) is physically manifested or expressed
Dominant gene:
A dominant gene is one that is expressed when it is present on only one of the chromosomes
Recessive gene
a recessive gene has to be present on both chromosomes to be expressed
X-linked inheritance:
A disorder caused by a mutation on the X gene, hence females are carriers, only males can have the disorder.
Homozygous:
A person with a pair of identical alleles for a particular gene locus
Heterozygous:
A dissimilar pair of alleles for a particular gene locus
Mutation
A change in the DNA sequence
Polymorphism
A frequent hereditary variation are a locus
Autosomal Recessive Inheritance
• Affected individuals born to (usually)
unaffected parents
• Either sex affected
• Carrier parents
• Increased incidence in consanguinous families
Autosomal Dominant Inheritance
Males and females equally affected
• Successive generations affected
• Disorder transmitted by both sexes
- Male to male transmission occurs
• Variable penetrance and expressivity
• New mutations common in some conditions
- may be no family history of the condition
• Child of affected parent has a 50% risk of inheriting the causative mutation
- variable penetrance and expressivity
Gene expression occurs in 2 ways?
Transcription and translation
Translation
• Transfer RNA (tRNA) molecules serve as interpreters during translation
-tRNA carries amino acid to Ribosome
• Transfer RNA (RNA) carries amino acid to Ribosome
• Reads 3 bases at a time
-Corresponding aminoacid is added to the Chain
A STOP codon causes the mRNA ribosome complex to fall apart
-Polypeptide chain folds forming protein
Mutations
Mutations can change the meaning of genes
• Mutations are changes in the DNA base sequence
- caused by errors in DNA replication or by mutagens
- change of a single DNA nucleotide causes sickle-cell disease
