7C- genotype and phenotype Flashcards
• the use of symbols in the writing of genotypes for the alleles present at a particular gene locus • the expression of dominant and recessive phenotypes, including codominance and incomplete dominance
diploid
having two sets 2n of each chromosome, one from each parent
homozygous
having identical alleles for the same gene on homologous chromosomes
heterozygous
having different alleles for the same gene on homologous chromosomes
dominant allele
the variant of a gene that masks the effect of a recessive allele on the same gene on a homologous chromosome
recessive allele
the variant of a gene that is masked by a dominant allele on a homologous chromosome
complete dominance
a pattern of dominance where only the dominant allele from the genotype of a heterozygous individual is expressed in the phenotype of that organism
phenotype
the physical or biochemical characteristics of an organism that are the result of gene expression (set of genes) and the environment
carrier
an organism that has inherited a copy of a recessive allele for a genetic trait but doesn’t display the trait due to it being masked by the presence of a dominant allele
genotype
the genetic composition of an organism at one particular gene locus, as represented using letter symbols
codominance
a pattern of dominance where both alleles from the genotype of a heterozygous individual are dominant and expressed in the phenotype of that organism
incomplete dominance
a pattern of dominance where neither allele from the genotype of a heterozygous individual is dominant and both are expressed in an intermediate phenotype
sex linked genes
genes that are located on a sex chromosome
x linked traits
a trait controlled by a gene that is located on the x chromosome
y-linked traits
a trait controlled by a gene that is located on the y chromosome
how many alleles do we inherit?
every diploid organism inherits a particular combination of two alleles from their parents
contrast homozygous and heterozygous cells?
in homozygous cells, an individual inherits two identical alleles from each parent whether its two dominant or two recessive.
contrast dominant and recessive alleles
a dominant allele is the stronger form of a pair of alleles and is represented with a capital letter. it will always be expressed (AA or Aa)
a recessive allele is the weaker form of a pair of alleles and is represented with a lowercase letter. can only occur if homozygous recessive
what occurs in heterozygous individuals?
complete dominance- a pattern of dominance where only the dominant allele from the genotype of a heterozygous individual is expressed in the phenotype of that organism
contrast genotypes and phenotypes
phenotypes are the physical/biochemical characteristics that are the result of gene expression and the environment
genotypes are the genetic composition of an organism at one particular gene locus, as represented using letter symbols
what is it called when there is a recessive allele in a heterozygous individual
although a dominant allele may mask the recessive allele, a person who is heterozygous at a specific gene locus is still a carrier→ can pass on the recessive allele to their offspring despite not displaying the trait
are dominant alleles more common than recessive?
no, for example the dominant trait is dwarfism
create a zygosity table- general table
zygosity | genotype
homo dom | AA
hetero | Aa
homo rec | aa
what is phenotype influenced by
genotype and the environment, making it susceptible to change over time
contrast codominance and incomplete dominance
codominance is when both alleles from the genotype are fully expressed in the phenotype of a heterozygote ( both are dominant and neither mask)
incomplete dominance is when neither allele is fully expressed in the phenotype of a genotype (blending of both alleles)
give an example of codominance
both red and white petals in a heterozygote
give an example of incomplete dominance
heterozygotes would display a mix of red and white forming pink
zygosity of codominance and incomplete dominance
homo option A- CACA
hetero- CACB
homo option B- CBCB
contrast x linked and y linked traits
X-linked traits a trait controlled by a gene that is located on the X chromosome- more likely to be found in males as they only have one X and will be expressed regardless. but can only be passed down to daughters
Y-linked traits a trait controlled by a gene that is located on the Y chromosome- thus only impacting males
genotypic variations for colour blindness
affected female- XbXb
unaffected female (carrier)- XBXb
unaffected female- XBXB
affected male- XbY
unaffected male XBY
why is colour blindness more common in men
because males only have one X chromosome, if they inherit the faulty gene that codes for colour blindness they will be colour blind. this is because they only have one X chromosome. lower chance for women
