Y10 Genetics Test

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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

1. enzyme commands the dna to unzip

2. 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)

3. this continues until the rna reaches a termination signal on the dna

4. 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)

1. I.P.M.A.T

2. 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.