science exam 1 yr 10

Meisher

isolated DNA

Franklin and Wilkins

produced DNA images

Chargaff

figured out base pairings

Watson and Crick

used this data to create a double helix structure

structure of DNA

structued as a double helix, made up of 2 long, antiparallel strands which are made of nucleotides which includes phosphate deoxyribose sugar and a nitrogenous base

base pairing

the bases include adenine, thymine, cytosine and guanine and the pairings are a=t and c=g

male karyotype

have X and Y chromosomes

female karyotype

have X chromosomes

purpose of DNA replication

growth and repair of muscle and bone tissues, create identical daughter cells from parent cells to ensure they function properly

process of DNA replication

helicase unwinds and breaks hydrogen bonds, polymerase builds a new strand of DNA using base pairings and only works in one direction making DNA antiparallel, end is 2 strands of DNA

purpose of protein synthesis

produce new proteins for hormonal functions, growth and development, structural support and metabolic and enzymatic function

structure of chromosomes

can be single or double stranded and arms are called chromatids, double stranded chromosomes are connected by a centromere

why cell needs to divide

for growth and repair of damaged tissues or muscles, for meiosis cell divides for reproduction

interphase

prepares for cell division by duplicating DNA an DNA is stored as chromatins

prophase

packages DNA into chromosomes, nuclear membrane breaks down, centrioles form spindle fibres

metaphase

chromosomes move to the metaphase plate and spindle fibres are attached

anaphase

spindle fibres pull chromosomes apart and chromosomes are pulled to opposite sides of the cell where they move to each daughter cell

telophase

DNA spreads out, 2 nuclei form, cell wall pinches to form 2 daughter cells where they make 2 new cells

importance of mitosis

growth and development, tissue repair and asexual reproduction

prophase I

DNA condenses into chromosomes, spindle fibres form, nuclear membrane dissolves, homologous chromosomes exchnage information through crossing over

metaphase I

chromosomes move to the metaphase plate, spindle fibres are attached, chromosomes line up in homologous pairs

anaphase I

sister chromatids remain attached as centrioles contract, each pair of homologous chromosomes separate

telophase I

two haploid cells form, each chromosomes still consist of 2 sister chromatids

prophase II

spindle fibres form, DNA condenses into chromosomes, nuclear membrane dissolves

metaphase II

chromosomes line up to the metaphase plate where spindle fibres are attached

anaphase II

centromere divide and sister chromatids move separately to each pole

telophase II

haploid daughter cells form as cell wall pinches in to form 4 daughter cells

haploid

having 1 complete set of chromosones, half number of chromosomes

diploid

having 2 complete set of chromosomes, full number of chromosomes

difference between meiosis I and meiosis II

meiosis I is where homologous chromosomes separate whereas in meiosis II sister chromatids separate

how meiosis and random fertilisation contribute to genetic variation

contribute to ensure each offspring gets a different combination of DNA

similarities in mitosis and meiosis

both need DNA replication, use separation of sister chromatids and use spindle fibres

differences in mitosis and meiosis division

mitosis has one while meiosis has two

differences in mitosis and meiosis cells

mitosis has generically identical cells while mieosis doesn't due to crossing over, independant assortment and random fertilisation

differences in mitosis and meiosis set of chromosomes

mitosis is diploid while meiosis is haploid

mendel

used peas to figure out homozygous and heterozygous alleles

law of segregation

each individual possesses 2 alleles, while split during meiosis resulting in each gamete carrying only one allele for the trait

law of independant assortment

genes for different traits are inherited independantly from one another

law of dominance

in a heterozygous, one allele may conceal the presence of another, making it the dominant allele

reginald c punnet

he made punnet squares which help us predict the phenotype and genotype of alleles

chromosomes

tightly coiled DNA

homologous

pair of chromosomes that contrain the same genes but the same DNA

fertilisation

when an egg meets a sperm

gamete

sex or reproductive cells

zygote

fertilised eff

gene

section of DNA that codes for a protein/trait

allele

form of gene

karyotype

laboratory image of chromosomes

locus

physical site of a gene

homozygous

having two identical alleles

heterozygous

having two different alleles

genotype

genetic appearance of a trait and can be found through punnet squares

phenotype

physical appearance of a trait and punnet squares are used to figure out if the individual has the trait or not

dominant

having more influence

recessive

having less influence

monohybrid cross

results in one prediction

pedigree

family tree of alleles

autosomal inheritance

passing of traits through autosomes

sex-linked trait

passing of traits through gametes

inheritance patterns

autosomal dominant, autosomal recessive, sex-linked dominant and sex-linked recessive

recessive trait

found when trait has skipped a generation or more

sex-linked ressive trait

found when the affected are mostly maes

polygenic inheritance

when an individual is affected by more than one allele

polygenic inheritance examples

eye colour, hair colour

fixed/free earlobes

are monogenic traits because a person have it or not

height

is polygenic traits as it is affected by many alleles

sex-linked inheritance punnet squares

are genes located on the sex chromosomes causing traits to differ between males and females

paley

argued the complexity of a human showed signs of god

lamarck

first to propose a comprehensive theory of evolution, arguing life was not fixed but evolved

darwin

developed natural selection to show how species change over time

wallace

developed natural selection independently

darwin vs lamarck

darwin's theory is more compelling than lamarck's because it was supported by evidence, explains inheritance through genetics and identifies variation that are passed to offspring

variation

individuals that differ from one another

overproduction

there are more individuals produced in a population than the environment can support

competition and survival of the fittest

environmental selection pressures favour those with more advantageous alleles, leading to competition where individuals with the advantageous alles survive compared to those without the allele

higher production rate

individuals with the inheritable advantageous alleles are more likely to survive, reproduce and have a higher reproduction rate compared to those without the allele

hertability

advantageous alleles are passed to offspring

allele frequency change

over consecutive generations, the frequency of the advantageous alleles increase while those with the allele decrease

evolution

process that results in cumulative, heritable changes in a population spread over many generations

mutation

change in gene or chromosome which may lead to new traits

how mutations result in formation of different alleles

result in different alleles through radiation or chemicals

natural selection

occurs when selection pressures in the environment confer a selective advantage over a specific phenotype to enhance its survival and reproduction

genetic drift

random, non-directional change in allele frequency between generations

gene flow

movement of individuals from one place to another

gene pool

total collection of alleles in a population

summerisation different stages of natural selection

variation happens when there are many species, which results in more individuals than the environment can support, leading to competition where they all fight for food. the individuals that survive make more individuals with their advantageous traits, leading to consecutive generations which make more individuals with their advantageous traits

dalton

proposed the atomic theory where matter is composed of small, invisible atoms

thomson

proved the atom was divisible and contained electrons

perrin

provided experimental proof to verify Einstein's theories

mendeleev

organised the 63 known elements based on increasing atomic weight and chemical properties

rutherford

conducted the gold foil experiment where he proved that the atom was mostly empty space except for the nucleus, proposing the nuclear model

moseley

refined the periodic table by connecting it to the atomic number

aston

provided proof that atomic weights were not always whole numbers

bohr

proposed that electrons occupy at fixed levels, providing a foundation for the electron configuration

chadwick

discovered a neutral particle later named as the neutron

period number (horizontal)

how may electron shells an atom has

group number (vertical)

how many valence electrons an atom has

reactivity

elements with nearly full/empty valence electron shells

valency

combining capacity of an atom that is determined by the number of electrons an atom gains or loses to achieve a stable electronic configuration

valence electrons

electrons on the outermost electron shell