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what is dna
deoxyribonucleic acid - it carries genetic instructions for growth, development, functioning and reproduction of organisms
structure of dna
described as a double helix (twisted ladder)
contains nucleotides, the building blocks of dna
the backbone of dna is made of sugar (ribose) and phosphate
nitrogenous bases (ATGC)
chromatin
tangled network of dna in the nucleus of a cell that isn’t dividing. dna in the cell is coiled around the nucleus to form chromatin
the 3 main parts of a nucleotide
sugar (deoxyribose)
phosphate group
nitrogenous base (A,T,G,C)
base pairs are bonded with a weak hydrogen bond
dna molecule is made up of thousands of nucleotides
nitrogenous bases
a = adenine
t = thymine
g = guanine
c = cytosine
describe structure of dna ribose(sugar)-phosphate backbone
the backbone of the dna molecule is composed of alternating sugar and phosphate groups
describe the purpose of weak hydrogen bonding
maintains structure of double helix
enables dna replication
accurately storing genetic info
how many chromosomes are in a healthy individual?
23 pairs - 22 autosomes (non-sex chromosomes), 1 sex chromosome.
karyotype
an individual’s set of chromosomes
healthy karyotype vs unhealthy karyotype
healthy karyotype shows the normal number and structure of chromosomes
unhealthy karyotype may show variations or abnormalities. can lead to genetic disorders/health conditions
describe relationship between dna, genes and chromosomes
dna is the molecular base of genetic information
genes are sections of dna that carry specific instructions (genetic code) for a specific characteristic.
chromosomes are structures made up of dna and proteins that organise and package genes.
these elements form the foundation of inheritance and expression of genetic traits in organisms.
what is rna
ribonucleic acid (rna) transmits genetic instructions from the dna in the cell nucleus to the ribosomes which are responsible for protein synthesis.
protein synthesis
joining of amino acid to make proteins
difference btwn dna and rna
dna: double helix
bases: adenine, guanine, cytosine, thymine
rna: single strand
bases: adenine, guanine, cytosine, uracil
types of rna
mRNA - messenger rna
tRNA - transfer rna
describe process of transcription
enzyme commands the dna to unzip
rna moves along the dna and matches RNA nucleotides with the exposed DNA bases (A with U, T with A, C with G, G with C)
this continues until the rna reaches a termination signal on the dna
dna is finally transcribed (copied) as mRNA
sexual vs asexual reproduction
sexual: involves two parents, genetic variation, and offspring are not identical to parents.
asexual: involves one parent, no genetic variation, and offspring are identical to parent.
examples of sexual reproduction
humans, flowering plants, animals, etc
examples of asexual reproduction
bacteria, yeast, fungi (molds)
mitosis
purpose: for growth and repair of cells
2 identical daughter cells produced
46 chromosomes beginning + end mitosis produces a full set of chromosomes, a diploid
stages of mitosis
5 phases: I.P.M.A.T
INTERPHASE: dna replication
PROPHASE: chromosomes thicken and centrioles appear, spindle fibre released
METAPHASE: spindle fibres direct the chromosomes to the middle of the cell
ANAPHASE: chromosomes separated, sister chromatids pulled to the poles/ends of the cell
TELOPHASE: nuclear membrane reforms around chromosomes, 2 new cells become apparent
meiosis
purpose: gamete production
4 non-identical daughter cells produced
46 chromosomes at start → 23 at end meiosis produces half a set of chromosomes, a haploid
stages of meiosis
(divide twice, because you do PMAT twice)
I.P.M.A.T
P2 M2 A2 T2
meiosis stage 1
interphase: dna replication
prophase 1: chromosomes thicken and spindle fibre forms, pairing of homologus chromosomes and crossing over → physical exchange of dna between pairs
metaphase 1: homologus pairs align along the middle in pairs
anaphase 1: chromosomes pulled away by spindle fibres to ends of the cell
telophase 1: ends w/ 2 newly formed cells
meiosis stage 2
prophase 2: chromosomes thicken and spindle fibers form
metaphase 2: chromosomes line up in the middle in single file
anaphase 2: chromatids pulled away by spindle fibers to poles of cell
telophase 2: the 2 cells divide and form 4 cells.
allele
alternative forms of a gene
BB = homozygous dominant
Bb = heterozygous
bb = homozygous recessive
homozygous
when you inherit the same alleles from each biological parent
e.g. BB = homozygous dominant
bb = homozygous recessive
heterozygous
when you inherit two different alleles from each biological parent
e.g. Bb = heterozygous
trait
a genetically determined characteristic
genotype
genetic makeup of an organism; the combination of alleles (e.g. BB, Bb, bb)
phenotype
physical characteristics/expression
chromatid
chromatids are the two identical strands of a chromosome, made of DNA.
chromosome
a thread-like structure found in the nucleus that consists of dna and proteins.
Note
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