protein synthesis and inheritance Flashcards
what is a diploid
a cell with 2 copies of each chromosome
how many chromosomes are in a human nucleus
46
what is a chromosome
thread like structure carrying genetic information
what is a gene
a series of chemical bases that codes for a specific protein
what is DNA
two strands coiled together to form a double helix
what are the four bases that hold a DNA strand together
adenine, thymine, cytosine, guanine.
the complementary base pairings are
AT and CG
what is a codon
a sequence of 3 DNA bases
describe the process of transcription
RNA binds to DNA, DNA unwinds and unzips, mRNA is produced from DNA. mRNA leaves the Nucleus, but DNA is too large to leave the nucleus
what is RNA
the enzyme involved in the joining together of base sequences to form mRNA
describe the process of translation
mRNA attaches to a ribosome, each codon of mRNA complementary to an anti-codon of tRNA. tRNA contains amino acids which bond together to form polypeptide chains.
what is asexual reproduction
involves a single parent and the offspring has identical genes to parent so there is no variation
describe Mitosis
a cell reproduces by splitting itself into two new cells which contain identical chromosomes
explain the process of mitosis
DNA forms x-shaped chromosomes, each arm being an exact duplicate of the other
cell fibres pull them apart, and the arms go to opposite ends of the cell
membranes form around each of the newly formed chromosomes, these become the nuclei, then the cytoplasm divides
what is haploid
e.g. gamete, they have half the number of chromosomes in a normal cell
what is sexual reproduction
fusion of male and female gametes, resulting in a mixture of genes and therefore more variation
describe the formation of a zygote into an embryo
fertilisation between male and female gametes fusion produces a zygote, this undergoes cell division by mitosis to produce an embryo
what is meiosis
produces 4 haploid cells which have non identical chromosomes
what happens in the first division of meiosis
cell duplicates it’s DNA, 1 arm of each x-shaped chromosome is an exact copy of the other.
the chromosomes line up in pairs in the centre of the cell
the cells are then pulled apart so each new cell has one copy of chromosomes (mixture)
creating genetic variation
what happens in the second division of meiosis
chromosomes line up in the centre of the cell and are pulled apart to form 4 haploid gametes
what is heterozygous
you have two different alleles for that particular gene
what is homozygous
you have two of the same alleles for that particular gene
what is codominance
when neither allele is recessive so you show characteristics from both alleles
what is genotype and phenotype
genotype is the alleles you have
phenotype is the characteristics they produce
