human biology 2026 notebook set

DNA

Deoxyribonucleic acid. It is the gentic material found in the nuclues of the cell. It carries the genetic codes. It determines all the characteristics of the living organism.

what is dnas structure

double helix structure

nucleotide

the units dna is composed of. DNA is nucleotides joined together. the nucleotides are antiparallel, so the other side will be the opposite.

what are nucleotides made out of

phosphate, sugar, nitrogenous base

DNA nitrogenous bases

thymine - adenine guanine - cytosine. different bases in different orders codes for different hair/eye colours

how are bases connected other

they are paired together with a hydrogen bond

cell division

new cells are constantly needed for growth and replacement of damaged and worn out cells

What are chromosomes made up of?

Tightly coiled up DNA

Where are chromosomes located?

In the nucleus of cells

What do different segments of DNA in chromosomes code for?

Different traits, such as eye colors

Can chromosomes be single stranded?

Yes, chromosomes can be single stranded

What is a double stranded chromosome?

A duplicate of the single chromosome

how many chromosomes are in each human cell

23 pairs of chromosomes, which is 46 single chromosomes. 22 pairs of chromosomes are autosomal and the 23rd pair is what determine what gender you are.

female chromosomes

XX

male chromosomes

XY

homologous chromosomes

the pair carry the same types of genes. They are placed in pairs due to their matching bands and size.

cell cycle

different phases cells go through to create new cells and do their jobs.

why is dna replication so important in the life of cells in your body

if no dna is made your body will not be able to make proteins. you need dna in cells, cells would be useless without dna.

somatic cells

the body cells in humans. arranged by 23 pairs of chromosomes and 46 single chromosomes

diploid cells

23 pairs of dna and 46 single strandes of dna

diploid number in humans

23 pairs of chromosomes and 46 single strands

chromosome

2 identical chromatids, centrometre and dna molecule

haploid cells

half the number of chromosomes 23 individual chromosomes

what cells are haploid

gametes sex cells

why do gametes need to be haploid

you get half of your chromosomes from your mum and the other half from your dad, 2 haploid cells equals one cell

haploid number in humans

23

mitosis

cell production for growth matenince and repair of the body

mitosis phases

(interphase)

prophase

metaphase

anaphase

telophase

PMAT

interphase

dna replication occurs, cell grows

prophase

chromosomes coil up, nuclues membrane breaks down, centroles migrate to opposite poles/sides

metaphase

chromosomes aline in the centre of the equator/middle, centrioles create spindles and join up with centromeres in chromosomes

anaphase

chromatids separte at centromeres, spindle reals them in to opposite poles

telophase

nuclear membrane reforms, spindles disappear, chromosomes unravel, but cells are still joined up

cytokinesis

division of the cells

what are the cells now created after mitosis

diploid, daugther, somatic, identical cells

meiosis

makes gametes with only 23 chromosomes, they are haploid. they do not make identical daughter cells

1st part of meiosis

diploid parent cell goes through interphase, then through PMAT and during metaphase the chromosomes line up differently to mitosis.

2nd part of meiosis

now there are 2 cells these cells now go through PMAT, without interphase and dna replication.

3rd part of meiosis

4 cells are now produced with 23 single chromosomes haploid cells.

cells created from meiosis

non identical daughter cells that are gametes

stages in dna replication

helicase

polyermase

ligase

helicase

separates the dna bases

polyermase

new nucleotides added to the bases glued bases together

ligase

joins new strands of dna together, glued phosphate on nuclotides together

What is epigenetics?

The changes in gene expression resulting from factors other than changes to the genes. genes can come in a switched on or switched off form.

What determines when, where, and which genes are switched on or off?

Epigenetics.

Can trauma affect gene expression?

Yes, trauma can cause certain genes to be switched off or on

protein synthesis

the creation of protein, transcription to translation

in protein sythesis what bases change

tymine has been switched with uracil. A now goes with U

transcription in protein synthesis

helicase separtes dna, bases join up in the middle with a copy of dna with polymerase. now there is a copy of dna. the message molecule leaves the nucleus. the dna then joins back together.

what is the copy of DNA in protein sythensis called

messenger RNA (MRNA)

where does translation happen in protein synthesis

in the ribosome in the cell

translation in protein synthesis phase 1

ribosome reads MRNA 3 nitrogenes bases at a time.

what is 3 nitrogenes bases on a MRNA called during protein synthesis

codon

what is a transfer RNA, TRNA

they have 3 bases they are called an anticodon, shapes on anticodon are different amino acids

translation in protein sythesis phase 2

3 bases on codon match with 3 bases on anticodon with complementary bases. then next 3 bases get read.

translation in protein sythesis phase 3

amino acids on anticodons then bond together with a peptide bond, then a protein is made with a chain of amino acids

allele

different versions of a gene, we have two alleles

dominant allele

an allele that is expressed in the phenotype

recessive allele

an allele that is only expressed when there is two of them. the 'weaker' allele

genotype

the combination of alleles. it is your genes

phenotype

the physical feature that is expressed

how to assigne the alleles

a capital letter is for the dominant trait and a lowercase letter is for the recessive trait

homozygous

2 of the same alleles

heterozygous

2 different alleles

what would Bb be

hetrozygous

what would BB be

homozygous dominant

what would bb be

homozygous recessive

punnent square

a chart that shows the possible outcomes of alleles from parents

what is the chance of being a boy or a girl

it is always a 50% chance, the sperm cell determines what gender you are.

what chromosome is bigger x or y

x chromosome

what is special about females and their chromosomes

if you are female you get a second oppotunity as the 2 x chromosomes both contain the same allele

what is special about male chromosomes

if you are male you dont have a second opputunity as the y chromosome is much smaller and cannot contain the same chromosomes.

what is a sex linked trait

the fact that women have a second chance as they have 2 alleles but males dont as the y chromosome is much smaller. this is found on chromosome 23.

punnent squares for sex linked traits

always use x and y chromosomes with the allele above it, for males only put the letter above the x chromosome and not the y

square

normal male

coloured in square

affected male

circle

normal female

coloured in circle

affected female

circle and square linked together

marraige

incomplete dominance

when both alleles are equal, with neither being dominant or recessive to each other. the allele will blend together

incomplete dominace example

a red flower is breded with a white flower, it creates a pink flower as the alleles blend together

codominance

traits are both equally dominat and both are equally expressed neither is recessive or dominant

codominace example

a red cow and a white cow are bred together, it creates a roan cow, a cow with an equal amount of white fur and red fur expressed, it does not make a pink cow.