B4 Flashcards
What is the simple definition of a gene
a unit of inheritance located at a particular locus of a chromosome
What is the detailed definition of a gene
A specific DNA sequence which codes for RNA + controls a particular characteristic or protein in an organism
what is an allele
an alternative form of a gene at a particular gene locus
What are alleles responsible for
responsible for determining contrasting traits of the same
character
How do alleles occur in different cell types
alleles occur in pairs in a diploid cell but only one is represented in a gamete
How do alleles position themselves on homologous chromosomes
they occupy the same relative positions on a pair of homologous chromosome
Define phenotype
the physical manifestation of a genetic trait that results from a specific genotype and its interaction with the environment
Define genotype
the complete genetic makeup of an organism (commonly referring to the paired alleles)
Define heterozygous
condition in which the alleles of a gene pair are different (e.g. Tt)
Define homozygous
condition in which the alleles of a gene pair are identical (= true / pure breeding)
- homozygous dominant (e.g. TT)
- homozygous recessive (e.g. tt)
What is homozygous dominant
TT
What is homozygous recessive
tt
Describe the dominant allele
A dominant allele expresses itself and gives the same phenotype in both the homozygous dominant and heterozygous conditions. (masks the influence of the recessive allele)
Describe the recessive allele
A recessive allele does not express itself in the heterozygous condition and only expresses itself in the homozygous recessive condition
What is the structure of a chromosome
rod-like structure visible in the nucleus during cell division
What is a chromosome made up of
made up of deoxyribonucleic acid (DNA)
What does DNA contain
DNA carries the hereditary information for making new organisms
What might each chromosome carry
each chromosome may carry many genes along its length
What is the nucleus in terms of genetics
The nucleus is the site of genetic material/chromosomes/genes in plant and animal cells
What is a monohybrid cross
Monohybrid cross: a cross between two pure-breeding organisms
What is monohybrid inheritance and how is this character controlled
an inheritance involving only one pair of contrasting traits
• The character is controlled by a single gene (a pair of alleles).
What are genetic diagrams used for
used to predict the traits that will be expressed by the offspring (genetic cross)
What happens if the trait is dominant on a pedigree
- Unaffected parents should not have affected children.
- Trait should not skip generations – affected individuals must have affected parent(s).
- When an affected individual mates with an unaffected individual, 50% of their offspring should be affected (heterozygous).
What happens if the trait is recessive on the pedigree
• If both parents are affected, all children should be affected.
• Unaffected parents can produce affected individuals.
• Trait often skips generations.
*Note: Most phenotypic features are the result of multiple genes rathe
What are phenotypic features due to
Most phenotypic features are the result of multiple genes rather than a single gene inheritance
