Intro and qualitative genetics Flashcards
What is a genome?
Total set of chromosomes in a cell
What are diploid chromosomes?
Genomes in which chromosomes are in pairs
What are homologues?
Two members of a homologous pair (in diploid chromosomes)
DNA is double stranded. What are the 4 nucleotides and which are purines and pyrimidines?
Adenine (purine)
Guanine (purine)
Cytosine (pyrimidine)
Thymine (pyrimidine)
What is a gene?
Segment of DNA coding for a polypeptide
mRNA does not have what feature?
Introns
What are introns and axons?
Exons = coding regions Introns = non-coding regions
What are mutations?
Alteration of nucleotide sequence
Mistake in DNA replication
What are examples of a point mutation?
Substitution of one nucleotide for another
Addition
Deletion
Mutations can be non-sense, missense or silent. What do these mean?
Non-sense= change of functional codon to stop/terminating codon Missense = single nucleotide change causes codon to code for a different AA Silent = no change to amino acid sequence
What is a loci?
Location of a gene on a chromosome
What is an allele? What is homozygous/heterozygous?
Different forms of the same gene
2 of the same alleles = homozygous
2 different alleles = hetereozygous
What is a genotype?
Particular combination of genes/alleles that an animal inherits
What is a phenotype?
What characteristic is measured/observed
What is codominance/additive gene action? How many possible genotypes/phenotypes can codominance lead to?
No allele is dominant to the other
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What is the First law of Mendelian’s inheritance?
Two alleles separate from each other in the formation of gametes
What is the Second law of Mendelian’s inheritance?
Genes for different traits assort independently of one another in the formation of gametes
What is epistasis? Give an example
The presence of an allele at one locus masks the effect of an allele at a different locus
Labrador colours: yellow, chocolate, black
What is inactivation? Give an example
One of the X chromosomes becomes inactive in each cell of female embryos during development
Tortoise shell cats = female
What are sex-linked genes?
Genes located on sex chromosomes
What are sex limited genes? Give an example
Autosomal genes affect a trait that is only shown by one sex (e.g. milk production)
What are autosomal genes?
Non-sex genes
What are sex-influenced genes? Give an example
The same genotype can lead to a different phenotype depending on the sex
E.g. horns in some breeds
What are single nucleotide polymorphisms?
Alleles that differ by a base substitution
Source of genetic variation
