inheritance (1) Flashcards
what is the definition of a chromosome?
a thread-like structure found in nucleus in which genetic information is organised in the DNA
(cell division: chromatin thread → chromosome)
what is the definition of a gene?
a basic unit of inheritance. it is a sequence of DNA nucleotides that codes for the formation of a single polypeptide
what is the definition of a gene locus?
the place on the chromosome where the gene resides (e.g. sequence of genes)
loci → plural
locus → singular
what is the definition of an allele?
alternative forms of the same gene. they are represented by letters
(e.g. B → black, b → brown)
what is the definition of a genotype?
genetic make-up of an organism. it is a set of alleles (e.g. B, b, R, r)
what is the definition of a phenotype?
outward and physical manifestation of an organism. it is influenced by the dominant allele (e.g. B or R)
what is a dominant allele?
an allele that is expressed in homozygous and heterozygous conditions (e.g. TT or Tt)
what is a recessive allele?
an allele that can only express itself in homozygous conditions (e.g. tt or rr)
what traits can you inherit?
- hair colour/type
- eye colour
- skin colour
- blood type
- ability to roll tongue
what is the definition of a progeny?
an offspring
what is the definition of a gamete?
a specialised reproductive cell that carries half the genetic information of an organism
(in a punnet square, the gametes must be circled)
what is a phenotype affected by?
it is affected by genes and environment (can play a part in the expression of genes)
how to find out if an allele is dominate or recessive?
test cross with homozygous recessive alleles (e.g. rr or tt)
what is a pedigree chart?
a family tree
what is a dominant pedigree?
where both parents are affected while one or more children is unaffected
what is a recessive pedigree?
where both parents are unaffected but one or more children are affected
how many chromosomes does each human cell have? (somatic)
23 pairs of chromosomes.
22 autosomes
2 sex chromosomes (either XY or XX)
how many chromosomes does a gamete have?
23 chromosomes.
22 autosomes
1 sex chromosome
(male: either X or Y, female: only X)
what is the genotype for phenotype A blood group?
AA or AO
what is the genotype for phenotype B blood group?
BB or BO
what is the genotype for phenotype AB blood group?
AB
what is the genotype for phenotype O blood group?
OO (O is recessive, only AB are dominant)
