Topic 3: Genetics Flashcards
What is chromosomes?
A long, coiled molecule of DNA that carries genetic information in the form of genes
What is a gene?
A section of DNA that codes for a specific sequence of amino acids which undergo polymerisation to form a protein
What are alleles?
Different versions of the same genes
What is a genotype?
An organisms genetic composition, describes all alleles
What is a phenotype?
An organisms observable characteristic due to interaction of the genotype and environment
What is homozygous?
Having two identical alleles of a gene
What is heterozygous?
Having two different alleles of a gene
What is a dominant allele?
Describes an allele that is always expressed, represented with a capital letter
What is recessive allele?
An allele that is only expressed in the absence of a dominant allele, represented with a small letter
What is monohybrid inheritance?
The inheritance of a single gene
What is the problem with single gene crosses?
Most characteristics are controlled by multiple alleles rather than just one
What are sex chromosomes?
A pair of chromosomes that determine sex
Why does the inheritance of a Y chromosome mean that an embryo develops into a male?
Tested development in an embryo is stimulated by a gene present on the Y chromosome
How can monohybrid inheritance be represented?
Punnet square and using a family pedigree
What is a sex-linked characteristic?
A characteristic that is coded for by an allele founded on a sex chromosome
Why are the majority of genes found on the X chromosome rather than the Y chromosome?
The X chromosome is bigger than the Y chromosome so more genes are carried on it
Why are men more likely to show the phenotype for a recessive sex-linked trait than woman?
Many genes are found on the X chromosome that have no counterpart on the Y chromosome and woman have two alleles for each sex-linked gene whereas men often only have one allele only one recessive allele is required to produce the recessive phenotype in males
What are the four different blood groups?
A, B, AB and O
What are codominant alleles?
Alleles that equally contribute to an organism’s phenotype, they’re expressed to an equal extent
What does AO give blood group A?
O is recessive to A, A is dominant and is expressed giving blood group A
What is the genotype for blood group O?
OO
What is sexual reproduction?
Type of reproduction, involves the production of gametes by meiosis, a gamete from each parent fuses to form a zygote and genetic information from each gamete is mixed so the resulting zygote is unique
What are gametes?
Sex and haploid cells
What is meiosis?
Form of cell division involved in the formation of gametes, chromosome number is halved and involves two division
What must occur prior to meiosis?
Interphase
What happens during the first stage of meiosis?
Chromosome pairs line up along the cell equator, the pair of chromosomes are separated and move to opposite poles of the cell (chromosome is pulled is random, creating variation) and chromosome number is halved
What happens during the second stage of meiosis?
Chromosomes line up along the cell equator, the chromatids are separated and move to opposite poles of the cell and four unique haploid gametes are produced