DGH: 1-7 Flashcards
Deoxyribonucleoc acid
a macromolecule that provides the instructions for making proteins
genome
all of the genetic material contained in an organism or a cell
karyotype
a display of the number and appearance of the chromosomes of an organism
DNA function
replication and protein synthesis
how DNA, chromosomes and genes are related?
a DNA molecule in cells is organised into coiled structures called chromosomes. DNA molecules wrap around histone proteins in order to fit into the nucleus. A gene is the basic unit of inheritance and is made up of DNA segments
Structure of DNA
DNA has a double helix structure, it is double stranded and the strands coil around each other like a twisted ladder
Nucleotide
made up of a deoxyribose sugar, a phosphate group and a nitrogenous base
Base pairs
Adenine and Thymine, Cytosine and Guanine
Prokaryotic DNA
in a circular ring in the nucleoid region of the cytoplasm. Also plasmids are smaller rings of DNA that have a limited number of genes
what is mitotic cell division for?
growth, repair and asexual reproduction
Somatic cells
normal body cells (not germ cells)
diploid
2N (chromosomes are in pairs)
Homologous pair
Pair of chromosomes that have the same genes in the same position but are different versions of the gene
Allele
versions of a particular gene (eg. blue eye colour)
what is meiotic devision for?
production of sex cells (gametes) and sexual reproduction
Haploid
N (one of the homologous chromosomes from parent cell)
Animal male gamete
Sperm (produced in testes)
Animal female gamete
eggs or ovum (produced in ovaries)
plant male gamete
pollen (produced in anther)
plant female gamete
egg cell (produced in ovary)
gamete
sex cell
centromere
place where sister chromatids join
DNA replication
the process by which a double stranded DNA molecule is copied to produce 2 identical DNA molecules
topoisomerase
enzyme that causes the double helix to unwind from histone proteins
DNA helicase
‘unzips’ the DNA molecule by breaking apart the hydrogen bonds (produces a replication fork)
Okazaki fragments
sections of replicated DNA
DNA ligase
joins okazaki fragments together
DNA polymerase
builds a new complimentary DNA strand by adding nucleotides in a 5’ to 3’ direction
DNA primase
provides a starting point for DNA polymerase to being synthesis of new DNA strand
characteristics of mitosis
no genetic variation in daughter cells, involves 1 nuclear division, maintains chromosome number, 2 daughter cells that are diploid
stages of mitosis
interphase, prophase, metaphase, anaphase, telophase, cytokinesis
characteristics of meiosis
halves chromosome number, 4 daughter cells that are haploid, involves 2 nuclear divisions, creates genetic variation
stages of meiosis
meiosis 1, meiosis 2
zygote
diploid cell that is a result of the fusing of 2 haploid sex cells
asexual reproduction
type of reproduction by which offspring arise from a single organism and inherit the genes of that parent only. It does not involve the fusion of gametes.
binary fission
division in half
mutation
the sudden changing of the structure of DNA
causes of mutations
errors in DNA replication, errors in cell division or exposure to mutagens
effects of mutations
in somatic cells, can lead to cancer. In sex cells, can be passed onto offspring
apoptosis
a gene that stops the daughter cells dying
nondisjunction
the failure of homologous chromosomes or sister chromatids to seperate properly during meiosis
mutagen
a physical, chemical or biological agent that changes the genetic material of an organism and thus increases frequency of mutations above the natural mutation rate
carcinogen
a mutagen known to cause cancer
SNP
single nucleotide polymorphism
silent mutation
no effect
missense mutation
a different amino acid to the original is brought into place, resulting in a protein that may be non-functional
nonsense mutation
the mutated base results in a ‘stop’ codon being introduced and this results in an incomplete protein being made
point mutation
single base in the DNA sequence is changed, one base is replaced by another
frameshift mutation
insertion or deletion of one or more nucleotides from within the original DNA sequence
neutral mutation
survival is unaffected
deleterious mutation
disrupts the function of the encoded protein diminishing the ability of the organism to survive
beneficial mutation
leads to a new allele that benefits the survival of an organism
transcription
when the DNA in a gene is copied to produce RNA
pre-mRNA processing
introns are removed, exons are spliced and a cap and tail is added
translation
when the code within the mRNA sequence is used to produce the amino acid polypeptide chain
introns
non-coding segments of DNA
exons
coding segments of DNA
gene expression
is when genes are ‘switched on’, ultimately ending in the production of a functional protein
structural proteins
provide the shape and structure of the cell ro carry out its function
functional proteins
specialised proteins which control the rates of reaction for the specific chemical reactions going on in each cell
phenotype
the characteristics of a cell and hence, the sum of the characteristics of an organism, that is determined by its protein expression
primary structure
unique linear sequence of amino acids in the ploypeptide chains that make a protein
secondary structure
coils or folds in ploypeptidde chains
tertiary structure
folding of the secondary structures into a complex and compacted shape
quaternary structure
the interaction between several polypeptide chains into one functional macromolecule
promoter
a short nucleotide sequence that signals the start of a gene
independent assortment
the process where the homologous chromosomes line up (assort) randomly at the equator and then move to seperate poles, independent of each other, during the first diversion of meiosis
types of mutagens
chemical, physical, biological
example of a physical mutagen
UV light, nuclear/ionising radiation
example of a chemical mutagen
mimics a nitrogen base, mustard gas, nitric acid
example of a biological mutagen
bacterial - crown gall
polyribosomes
ribosomes that occur in chains all binding to a single mRNA strand. Allows a large number of polypeptides to be made from a single strand in a short time
genotype
set of genes in our DNA which is responsible for particular traits
phenotype
the physical expression, or characteristics, of a trait
factors that influence phenotype
temperature, light, soil pH
how is variation created in sexually producing organisms
meiosis (independent assortment and crossing over), fertilisation, germ cell mutations
independent assortment
process where homologous chromosomes line up randomly at the equator and move to seperate poles, independent of each other
No. of different combinations of zygote?
2 to the power of n
crossing over
when chromosomes pair up, sections of chromatids on adjacent chromosomes will swap places
