Heredity Flashcards
What is heredity?
The passing of characteristics from a generation to another through shared dna
Who is considered the father of modern genetics?
Gregor Mendel
What did Gregor Mendel do?
He bred purebred pea plants in a garden, and came up with a theory of heredity before dna was known about
What are genes?
segments of dna that code for a specific trait
What are alleles?
Different versions of a gene
Give an exmaple of a gene and allele
gene:eye colour
allele:blue vs brown
What are genes carried on?
Homologous chromosomes
When are homologous chromosomes inherited?
From each parent after fertilisation
What are homologous chromosomes like?
they have the same genes arranged in the same order, but slightly different dna sequences
What kind of alleles do homologous chromosomes contain?
Different alleles, and those combinations determine the final trait
What do our genes code for?
An enzyme called tyrosinase
What does tyrosinase make?
melanin; skin colour
What would happen if there’s a mutation in the dna that makes the tyrosinase enzyme?
the person wouldn’t be able to make skin pigment (albinism)
What is a dominant trait?
a trait expressed when an individual posses either one or two copies of the dominant allele
What can dominant traits do?
They have the ability to suppress the expression of their recessive counterpart
1 dominant allele
2 dominant allele
dominant trait
2 recessive allele
recessive trait
What is a homozygous individual?
Has 2 identical alleles for a gene located at the same locus (position) on homologous chromosomes
What is another word for heterozygous?
hybrid, carrier
What is a heterozygous individual?
Has 2 different alleles for a gene (1 dominant, 1 recessive)
What’s a genotype?
a specific genetic info of an organism, with regards to a set of traits
What does genotype represent?
The combination of alleles an individual possesses for a gene
What’ a phenotype?
an expression of an individual’s genes in terms of traits that can be seen or measured
Why do dominant/recessive traits exist?
due to gene mutations
Why do recessive traits exist?
due to a lack of protein/protein not being produced properly
Why are wrinkled seeds wrinkled?
due to a dna mutation that doesn’t create an enzyme to make starch
What are mendel’s laws of heredity?
law of dominance, law of independent assortment, law of segregation
What’s the law of dominance?
dominant alleles mask the expression of recessive alleles when they’re present together in heterozygous. Only when an individual is homozygous for the recessive trait will the recessive trait be expressed.
What’s the law of independent assortment?
genes located on different chromosomes assort independently of each other during gamete formation. (The inheritance of one gene doesn’t influence the inheritance of another gene located on a different chromosome)
What’s the law of segregation?
Individuals inherit 2 alleles for each gene, one from each parent. These alleles segregate during the formation of gametes, ensuring that each gamete carries only one allele for each gene
What happens when 2 organisms mate?
Their gametes and alleles come together randomly to produce offspring
What are punnett squares?
they’re used to express the law of segregation and show how gametes pair at random
What does the punnett square show?
the probability that offspring will have a certain phenotype/genotype
