Variation And Inheritance Flashcards
What is a Gene?
A gene is a section of DNA that codes for a species that codes for a specific protein. It is the unit of heredity, and can be copied and passed on to the next generation
What does P/F1/F2 mean?
Parents/ First generation of offspring / second generation
What is a Phenotype?
The appearance/characteristic of an organism e.g. tongue roller, albino
What is a Genotype?
The genetic make_up of an organism, indicated by two symbols e.g. “TT” , “aa”
What is the genotype of a gamete?
The genetic make-up pf the gamete, indicated by one symbol e.g. “T” , “a”
What are Alleles?
The different forms of a gene, e.g. “A” and “a” are Alleles for the gene of albinism, while “T” and “t” are the Alleles for the gene for tongue rolling
What is Homozygous (True breeding)
The two Alleles are the same e.g. “TT” or “tt”, ”AA” or “aa”
What is Heterozygous (Hybrid)
The two Alleles are different e.g. “Tt” or “Aa”
What is a Dominant gene?
The allele that shows in the phenotype of the heterozygote, e.g. “Tt” is a tongue roller, so the tongue rolling Allele must be dominant over the non-roller Allele
What is a Recessive gene?
The Allele that is masked in the heterozygote e.g. “Aa” has normal pigmentation, so the Allele for albino must be recessive
What is Polygenic Inheritance?
Several genes are involved in the inheritance of a characteristic. This means there is a range of phenotypes showing continuous variation e.g.. heights and skin colour in humans, mass of seeds in plants. There’s a maximum, and a minimum. Polygenic inheritance is responsible for most features of an organism’s phenotype
What is Monohybrid Inheritance?
A single gene controls a phenotype, e.g. attached ear lobes/unattached ear lobes. This will result in discrete variation. Measurements fall into distinct groups
What is Discrete Variation?
Discrete variation is where measurements fall into distinct groups or categories.
What graph do we use to show discrete variation?
A bar graph
What type of inheritance is it that measurements fall into distinct groups?
Single gene inheritance/Monohybrid inheritance
What is continuous variation?
Continuous variation is where a characteristic can have any value over a range, from minimum to maximum.
What graph do we use to show continuous variation?
A histogram
What type of inheritance is it that shows continuous variation?
Polygenic inheritance
How does variation occur?
Combining genes from two different parents
At so we use to explain inheritance?
Punnett squares
Why are predicted phenotype ratios among offspring not always achieved?
Fertilization is a random process
sample size being too small
