yr10 biology exam revision

purpose of mitosis

growth
recovery from injuries/illnesses

where does mitosis occur

bodily/somatic cells

purpose of meiosis

to create gametes for sexual production with half the genetic material of the parent cells

where does meiosis occur

somatic cells

examples of where meiosis occurs

males = sperm
females = eggs/ova

what does mitosis result in

identical cells that replace what was lost and replace old cells with young cells

goal of mitosis

to ensure each daughter cell receives a full set of chromosomes

process of mitosis overall

a single parent cell divides to produce 2 identical daughter cells with diploid genomes

process of meiosis overall

single diploid parent cell divides to produce 4 different daughter cells with haploid genomes

process of meiosis example overall

when a sperm and an egg join in fertilisation, the two haploid sets of chromosomes form a zygote with a complete diploid set: a genome

common process of meiosis and mitosis

interphase

explain interphase

cells grow, replicate chromosomes, prepare for cell division

chromosome pairs in humans

23

total chromosome number in a human

46

number of chromotids in a human

92

genetics meaning

study of heredity

heredity meaning

the transfer of characteristics from one generation to another

what is each characteristic determined by

one from each parent

genetype meaning

genetic makeup of an organism

phenotype meaning

expression of genes/characteristics displayed

gene meaning

encodes the info for a particular characteristic

allele meaning

alternative form of a gene

homozygous meaning

an individual carries the same allele on both the inherited mother and father's chromosomes

sex chromosome of female

xx

sex chromosome of male

xy

karyotype meaning

the arrangement of homologous pairs of chromosomes

cause of chromosomal abnormalities

having an extra copy of a chromosome = extra genes = extra protein than required
+
having fewer copies of a chromosome = fewer genes = fewer protein than required

what do proteins do

perform functions in a cell and controls its traits

effect of excess protein

can interfere with other cellular processes

effect of lack of protein

does not allow for protein to function properly

what affects proteins function

type and amount of protein

what happens when proteins don't function properly

reflected in their phenotypes: physical/intellectual differences

what happens when an unusual number of chromosomes fertilises another gamete

the resulting zygote will have an unusual number of chromosomes

purpose of pedrigrees

to identify if a trait is genetically inherited
trace the occurrence of a genetic disorder
predict the likelihood of a family member inheriting a genetic disorder
deduce the genotype of an individual

limitation of pedigrees

useful only if the organism does not produce too many offspring
requires accurate and reliable record keeping
could result in ambiguous conclusions if a family is small and too affected

x linked recessive trait

more males affected
sons of carrier mothers at higher risk
can skip generations

x linked dominant trait

can affect both males and females (more frequent in females)
fathers pass to all daughters

autosomal dominant trait

affects males and females equally
50% chance of inheritance from an affected parent

autosomal recessive trait

may appear to skip generations
siblings of affected child have a 25% risk

DNA meaning (CHONP)

a nucleic acid consisting of carbon, hydrogen, oxygen, nitrogen, phosphorus

complementary base pairings

AT, GC

what part of the nucleotide is the circle

phosphate

what part of the nucleotide is the pentagon

deoxyribose sugar

what part of the nucleotide is the rectangle

base

what holds the bases together

hydrogen bond

process of dna replication

parent dna molecule
hydrogen bonds break, dna breaks into 2 strands
each strand acts as a template and a new complementary strand of dna is formed
two identical daughter dna molecules

gene mutation meaning

permanent alteration in the nucleotide sequence of dna

effect of mutations

harmless unless they lead to cell deaths/tumours/cancers

how are hereditary/germline mutations inherited

from a parent

where are hereditary/germline mutations present

present in parent's eggs or sperm cells
+
present throughout person's life in every cell of body

how do aquired/somatic mutations occur

at some point during a person's life, caused by environmental factors

causes in gene mutations

errors in dna replication/recombination - rearranged dna
chemical damage - structure change of nucleotides
uv radiation - mismatched base pairs

codon length

3 nucleotides long

start codon

AUG

stop codon

UAA
UAG
UGA

types of dna mutations

base substitutions
insertions
deletions

types of base substitutions

silent
nonsense
missense

silent base substitution meaning

some codons code for the same protein, no observable effect

nonsense base substitution meaning

sequence no longer makes sense

missense base substitution meaning

sequence makes sense but codes for something else

insertion base meaning

insertion of bases shift the frame to altered groups of 3

deletion base meaning

deletion of bases shifts the frame to create altered groups of 3

dna mutation effect types

no effect
deleterious
advantageous

which dna mutation effect is the most common

deleterious

which dna mutation effect is the most rare

advantageous

deleterious mutation effects

affects a gene, stopping it from functioning or controlling properly, harming the organism

example of deleterious mutation effect

sickle cell anemia

advantageous mutation effects

gene enhances its function or control, to the benefit of the organism

example of advantageous mutation effect

lactase gene

gmo meaning

an organism whose genome has been altered in the laboratory to favour the expression of desired traits, often involves the insertion of genetic material from another species

selective breeding meaning

choosing parents with particular characteristics to breed together and produce offspring with more desirable characteristics

advantage of gm foods/crops

no difference among animals eating gm plants
gm foods have been eaten by millions worldwide for more than 15 years, with no ill effects

disadvantage of gm foods/crops

gm crop genes can spread to weed plants, making them resistant to herbicides
humans can accidentally eat gm foods intended for animals

whole organism cloning meaning

the creation of an exact genetic copy of the whole organism

gene cloning meaning

isolating and making multiple exact copies of a specific gene/segments of dna of an organism

recombinant dna technology

using enzymes and other laboratory techniques to isolate and manipulate dna segments of interest

what is recombinant dna technology used for

creation of gmos
manufacture of pharmaceuticals/vaccines
genetic research in university labs

gene therapy meaning

treatment of disease by transfer of healthy genetic material into cells to replace disease-causing genes

example of what gene therapy can be used for

cystic fibrosis

stem cells meaning

unspecialised cells that have the potential to become specialised

types of stem cells

embryonic
adult
induced pluripotent (IPS)

embryonic stem cell meaning

stem cells that can become any type of cell in the body

what does embryonic stem cells use

uses embryos that are a few days old

what do embryonic stem cells involve

killing a donated embryo

adult stem cell meaning

can become any of the cell type of the tissue they are found in

example of adult stem cells

stem cells in brain marrow can become blood cells

where are induced pluripotent cells found

in specific adult tissues and organs

where are induced pluripotent cells derived from

skin/blood cells

what can induced pluripotent cells develop into

unlimited source of any type of human cell

what have induced pluripotent cells been reprogrammed into

embryonic like state