inheritance Flashcards
what is inheritance
The transmission of genetic information from generation to generation
what is a chromosome
a thread of DNA, made up of a string of genes
what is a gene
a length of DNA that is the unit of heredity and codes for a specific protein. A gene may be copied and passed on to the next generation
what is an allele
any of two or more alternative forms of a gene
what is a haploid nucleus
a nucleus containing a single set of unpaired chromosomes (e.g. sperm and egg)
what is a diploid nucleus
a nucleus containing two sets of chromosomes (e.g. in body cells)
inheritance of gender in humans
woman’s gamete can only carry an “X” chromosome, and a male gamete can carry either an “X” or “Y” chromosome; females are “XX” while males are “XY”. There is always a 50% chance of getting a boy and vice versa.
function of DNA
control cell functions by controlling production of proteins, antibodies and receptors for neurotransmitters
makeup of DNA
DNA has 2 long strands and 4 nucleotides, AT and CG
process of protein synthesis
Made from long chains of amino acids (20)
DNA bases are read as triplets
DNA is found in the nucleus
Protein synthesis happens on ribosome in cytoplasm
mRNA carries information from DNA to ribosome
When a protein is made, mRNA is made in the nucleus, copying the base sequence
mRNA moves out of the nucleus into the cytoplasm and attaches to the ribosome
ribosome assembles amino acids into protein molecules
the specific order of amino acids is determined by the sequence of bases in the mRNA
why are some genes in particular cells not present
All body cells in an organism contain the same genes, but many genes in a particular cell are not expressed because the cell only makes the specific proteins it needs
what is mitosis
The nuclear division giving rise to genetically identical cells in which the chromosome number is maintained by the exact duplication of chromosomes.
what is mitosis needed for
Growth: in animals each tissue provides its own new cells when they are needed.
Repair of damaged tissues: for example, when you cut your skin, mitosis provides new cells to cover up cut.
Replacement of worn out cells
Asexual reproduction: in plants
what are stem cells
unspecialized cells that divide by mitosis to produce daughter cells that can become specialized for specific functions
what is meiosis
Reduction division in which the chromosome number is halved from diploid to haploid
Gametes are the result of meiosis
Meiosis results in genetic variation so the cells produced are not all genetically identical.
what is a genotype
genetic makeup of an organism in terms of the alleles present (e.g. Tt or GG)
what is a phenotype
physical or other features of an organism due to both its genotype and its environment (e.g. tall plant or green seed)
relation between genotypes and phenotypes
genotype + environment + random variation → phenotype
what is homozygous
having two identical alleles of a particular gene (e.g. TT or gg). Two identical homozygous individuals that breed together will be pure-breeding
what is heterozygous
having two different alleles of a particular gene (e.g. Tt or Gg), not pure-breeding
what is dominant
an allele that is expressed if it is present (e.g. T or G)
what is recessive
an allele that is only expressed when there is no dominant allele of the gene present (e.g. t or g)
what is codominance
when neither of two alleles is dominant to each other.
what are the blood group alleles
There are three alleles for blood group given by the symbols I^a, I^b and I^o.
I^a and I^b are co-dominant giving blood group AB or I^aI^b, and both dominant to I^o.
what is a sex-inked characteristic
a characteristic in which the gene responsible is located on a sex chromosome and that this makes it more common in one sex than in the other
Colour blindness as an example of sex linkage
