task 1. Flashcards
define cell replication
the process by which cells replicate their genetic material and divide to form new cells.
define mitosis
mitosis is a type of cell division where 1 parent cell divides once to produce 2 identical cells.
what is the result of mitosis
2 identical daughter cells
describe the prophase in mitosis
chromatin shortens and thickens to form chromosomes
order of the phases in mitosis
prophase metaphase anaphase telophase cytokinesis
describe the metaphase in mitosis
chromosomes line up individually
describe anaphase in mitosis
spindle fibres attach to centromeres
describe telophase in mitosis
spindle fibres shorten, centromeres break and chromatids move apart
describe cytokinesis
cytoplasm separates, cell and nuclear membrane from chromosomes uncoil
importance of mitosis
creates new body cells that is needed for growth, repair and maintenance
what are the 3 steps in dna replication
- unravelling the dna
- building a new strand
- forming the dna backbone
explain the unravelling of the DNA as part of dna replication
the enzyme DNA helicase breaks the hydrogen bonds between the bases, “unzipping” the double helix into single strands
explain the building a new strand as part of dna replication
“semi conservative” process. When DNA is produced, one of the strands in each new DNA moleucle comes fromt he old DNA molecule - reduces the chance of copying a strand incorrectly - dna polymerase helps bind free nucleotides in the cell nucleus to the single strands - meaning an identical copy of the dna strand is produced
explain the formation of the dna backbone as part of dna replication
dna polymerase stitches these newly joined nucleotides together so that the sugar-phosphate backbone is formed.
what is transcription
an mRNA copy of a gene is made and DNA is used as a template
explain the steps of transcription
- rna polymerase attaches to dna at the desired gene and separates the strands to expose the nucleotides in that region
- one strand is used as a template to make mRNA strand identical to the other strand, through complementary base pairings
- free floating nucleotides pair with their complementary bases on the template strand
- the rna polymerase reaches a stop codon and lets go of the DNA strand (production is complete for prokaryotes)
- in eukaryotes, introns are spiced out of the strand and exons are stuck together to form the final mRNA strand.
- mrna molecules leave the nucelus and enter the cytoplasm through nuclear pore
what is translation
mRna is converted to a polypeptide chain
steps of translation
- mrna attaches to a ribosome at a particular start codon
- the mrna molecule is with the correct anticodon pairs up with he mRNA in the ribosomes
- a second tRNA molecule attaches to the next codon on the mRNA strand
- the ribosome catalyses the formation of a peptide bond between the two amino acids
- the ribosome continues to the move along the mrna until is reaches a stop codon
- the polypeptide chain and mrna strand are released from the ribsome.
what is incomplete dominance
two dominant alleles resulting in a blended phenotype
e.g. of incomplete dominancę
red flower x white flower = pink hetero flower
what is codominance
two dominant alleles resulting in both phenotypes being expressed athe the same time
e.g. of codominance
black chicken x white chicken = heterzygous having both black and white feathers
what is sex linked
when an allele is located on the x chromosome
e.g. sex linked
haemophilia or colour blindess
