Genetic inheritance Flashcards
What is a gamete
reproductive cells of parents - sperm and ova
has 23 chromosomes
What is zygote
new cell formed by conception
contains full complement of DNA [half from sperm, half from ova]
What is role of DNA?
to give genetic information in each cell
What are genes?
segments of DNA that code for individual traits
What are chromosomes?
Storage structures for DNA
rod like structures visible in cell nucleus
46 chromosomes [in 23 pairs]
What is mitosis?
creation of new cells
each chromosome replicates to form two chromosomes with identical genetic blueprints. As cell divides, one member of each pair becomes a member of each daughter cell. Complete genetic endownment is replicated across almost every cell.
What is meiosis?
halves number of chromosomes in cell.
Chromosomes pair up and copy, then break into smaller pieces before ‘crossing over’ [randomly exchanging material] and creating new chromosomes with new hereditary combinations.
New chromosomes divide into two separate cells, then again to create 4 cells.
each has unique genetic material
each has 23 chromosomes.
What is genotype?
specific genetic information a person inherits that has the potential to influence their observable physical and behavioural characteristics
What is phenotype?
traits as displayed or expressed [genotype + environment]
What is dominant gene?
influences a child’s phenotype even if paired with a recessive gene
What is a recessive gene?
Will only influence a child’s phenotype if paired with another recessive gene
What are alleles
two alleles for each gene. Different alleles produce variation in inherited characteristics
What are homozygous genes?
alleles for a trait are identical
what are heterozygous genes?
alleles for trait are different
What are polygenic traits
most traits are polygenic - rely on many genes
How many male zygotes are formed at fertilisation, as compared to female?
30% more
How many male babies are born, cf female
6%
What causes vulnerability to male babies?
could be that X chromosome [longer than Y] holds more genetic information, and therefore if there is a weakness can’t be compensated by other gene on Y
What are four genetic abnormalities
chromosome abnormality
dominant gene disorders [eg huntingtons]
recessive gene disorders [eg sickle cell disease]
multifactorial [polygenic] - congenital disease
What is downs syndrome?
Trisomy 21 - extra 21st chromosome
What is PKU?
phylketonuria, recessive disorder - two recessive alleles, can’t process proteins. leads to low level intellectual disability. can be influenced by diet
What is genetic counseling?
helps parents assess risk of bearing child with genetic defect
What is behavioural genetics?
study of nature/nurture interaction
What is Range of Reaction in behavioural genetics?
range of possible phenotypes - depends on environment
