Topic 6- inheritance, variation and evolution

What does DNA stand for

Deoxyribonucleic acid

Define DNA

DNA is a polymer made up of 2 strands forming a double helix that carries genetic information

Define Chromosomes

Thin, long strands that are made from DNA

how many chromosomes are in body cells

46 chromosomes

how many chromosomes does a gamete cell have

23 chromosomes

what are the 23rd chromosomes

sex chromosomes

Define a gene

short lengths of DNA that codes for a particular sequence of amino acids which form a protein

define a nucleus

where DNA/genetic material is stored

how many different types of amino acids are there

20

what does a gene determine

determines what proteins the cell produce which decides what type of cell it would be

define a Genome

is the entire set of genetic material in an organism

what do genes allow scientist to do

allows scientist to identify genes in the genome that are linked to different types of disease

what’s another thing scientist can use genomes for

to trace migration of certain populations and ancestors around the world.

how are scientist able to use genomes to trace ancestors

The human Genome is mostly identical in all individuals so small differences tell us when they separated such as when humans left Africa

What does each nucleotide consists of

consists of one sugar molecule, one phosphate molecule and one ‘base’

what is each amino acid coded for?

coded for by a sequence of three bases in the gene

Give a few examples of some types of protein

-enzymes which act as a biological catalyst to speed up chemical reactions in the body

-hormones which are used to carry messages around the body

define an allele

are different versions of the same gene

if alleles are the same what are they called

homozygous

if alleles are different what are they called

heterozygous

what 2 types of alleles are there

dominant and recessive

what is a dominant allele

Dominant allele are always expressed (capital letter) and only need one copy

what’s a recessive allele

only expressed if there is 2 copies

define a genotype

the alleles that code for a particular characteristics e.g. dominant or recessive

define phenotype

the physical/observable characteristics of an organism so is the characteristics you get from a genotype

what is a diploid cell

cell containing two copies of each chromosomes (46)

what’s a haploid cell

cell containing one complete set of chromosomes (23)

define a zygote

zygote is formed at fertilisation when a sperm and egg fuse

what are 2 ways for reproduction

asexual and sexual

what’s sexual reproduction

is where genetic information from two organisms combine/fuse their gametes to produce offspring which are genetically different and they inherit characteristics

what process happens during sexual reproduction

meiosis

what is asexual reproduction

when there’s only 1 parent so produces genetically identical cells which happens through mitosis

how do prokaryotic organisms reproduce asexually

by binary fission

how are gametes produced

produced by meiosis (gametes are haploid cells)

what’s the process of meiosis

1-cell replicates/duplicates its genetic information / chromosomes forming 2 arms

2-chromosomes line up along the centre of the cell in their pairs

3-chromosomes are pulled apart to the side and the cell splits in two- chromosomes are randomly distributed e.g. one may have more maternal chromosomes making it genetically different

4- 2nd division- chromosomes line up in the cell again and each arm of the chromosome are pulled apart and the cell divides again making 4 cells which are genetically different and have 23 chromosomes in each

the cell produced by gamete fusion replicates itself

-after 2 gametes have fused during fertilisation, the resulting in new cell divides by mitosis to make a copy of itself

-mitosis repeats many times to produce lots of new cells in an embryo

-as embryo develops the cells start to differentiate into different types of specialised cells that make up a whole organism

what are the advantages of sexual reproduction over asexual

-offspring has a mixture of two sets of chromosomes which produces more variation

-variation increases chance of species surviving a change in the environment (survival advantage)

-because they have a survival advantage they are more likely to breed successfully the better adapted species= natural selection

what are the advantages of asexual reproduction over sexual

-only needs one parent, less energy , much faster, many identical offspring can be produced in favourable conditions

what two chromosomes makes a male

XY

what two chromosomes makes a female

XX

Eggs will always have what chromosome?

X

what chromosome will sperms have?

50% chance of X and 50% chance of Y

What are the two types of variations

genetic and environmental variations

everyone in the world has what…. (proteins +genes)

everyone has different combinations of proteins in their genes so will look different

what are most of our characteristics determined by

by the interaction of our genes and our environment

what creates genetic variation

when an egg and sperm cells fertilise and form an embryo which creates a new organism that organism will have genes that they have inherited from their mother and father but these genes will be random meaning not everyone has the same which creates genetic variation

give examples of characteristic determined by genes only

eye colour, blood group, inherited disorders

give examples of characteristics determined by a mixture of genetic and environmental factors

body weight, height, academic or athletic prowess, skin colour

why is there so much genetic variation

due to mutations

what are mutations

are changes to the sequence in the DNA code meaning that the protein it codes for may be different and can sometimes be inherited

when do genes mutate

it is a random change that occur continuously and spontaneously

how do mutations lead to changes in the protein that code for the DNA

as sequence of DNA bases codes for the sequence of amino acids that make a protein as DNA sequence changes so does protein code

what’s the two different effects a mutation could have on a protein

• little/no effect on protein will small extent of change

• seriously effect causing protein to change shape affecting its ability to perform as shape of enzymes active site is changes meaning substrate cant bind to it

mutations could rarely result in a new …..

phenotype in species

some mutations are beneficial others are

bad and unwanted

what’s the theory of evolution

all of todays species have evolved from simple life forms that started to develop over 3billion years ago leading to new species or change in species

what did Charles Darwin come up with

he came up with the theory about evolution which he called survival of the fittest

what did Charles Darwin not know about at the time

did not know about mutations or genes

why and how did Charles Darwin come up with this theory - and what was his proper name for it

• he knew organisms in a species showed wide variation and organisms have to compete for limited resources in an ecosystem

• therefor he concluded that organisms with the most suitable characteristics for the environment would be more successful competitors and more likely to survive + reproduce which passes on their useful traits

• and that organisms less well adapted where less likely to survive and reproduce which reduces their bad genes meaning overtime more organisms/species would have inherited the useful genes = evolve to survive

• This was called natural selection

why did it take a long time for his theory to be accepted

due to lack of evidence, went against religion as the theory of creation by God and lastly did not know about genes, DNA and mutations at the time

how was Charles Darwin’s theory proven

due to fossil records and the discovery of genes/DNA with phenotypes and genotypes

How did phenotypes prove Charles Darwin’s theory

over time the phenotypes of two different populations within a species would become so different they can no longer interbreed to produce fertile offspring at which point a new species is formed

what is it called for a development of a new species

speciation

define fossils

the remains of plants and animals/dead organisms from thousands of years ago which are found in rocks

what evidence to fossils provide

evidence that organism lived ages ago which are now extinct so show how much or little organism have evolved / changes so is evidence for evolution

what are the 3 main types of fossils

• gradual replacement by minerals

• from casts and impressions

• preservation

how are fossils formed in gradual replacement by minerals

things like teeth, bones and shells that decay really so last a long time when buried and eventually get replaced by minerals as they decay forming a rock-like substance shaped like the original structure which provides a perfect model

how are fossils formed from casts and impressions

fossils can be formed when an organism is buried in a soft material e.g. clay, the clay later hardens around organism as it decays leaving a cast of itself or an animals burrow/plant roots can be preserved as casts. Thins like footprints can be pressed into soft materials leaving an impression when it hardens.

how are fossils formed from preservation

preservation is where there is no decay- organisms get stuck in amber or tar pits there’s no oxygen or moisture so decay microbes cant survive to decay such as in glaciers its too cold or beat bogs too acidic. Causing remain completely intact.

why are there still periods where we don’t know what happened and how life first developed

because early life forms where soft bodied meaning they decayed quickly and completely and or fossils formed so long ago have been destroyed by geologic activity= movement of tectonic plates

what is extinction

when no individuals of a species remain

what are the reasons for extinction

• environment changes too quickly so cant adapt

• a new predator kills them all

• a new disease kill them all

• cant compete with another (new) species for food

• catastrophic event that kills them

what is selective breeding

is when humans artificially select plants of animals that are going to breed so that the genes for particular characteristics remain in the populations. Organisms are selectively bred to develop features/ characteristics that are useful or attractive

what is the process of selective breeding

-take a look at individuals in existing stock and select the ones which have the desired characteristics you are after

-breed them with each other

-select the best of the offspring and breed them together

-continue this process of picking the best/ most desired and reproduce them causing the desirable traits to get stronger and stronger and eventually all of the offspring will have the characteristic

draw backs to selective breeding

-reduces the gene pool of the population- the number of different alleles (forms a gene) in a population because when we are selectively breeding we are selecting for certain alleles that code for the traits we want meaning that we will have a smaller pool of alleles. By breeding them together which are closely related this can cause inbreeding.

-Inbreeding- can cause health problems and make organisms prone to disease of inherited disorders/ harmful genetic defects as gene pool is limited.

-less variation in population as they are closely related so if a new disease comes it can kill all of them

-less chance of any resistant alleles being presented in the population

what is genetic engineering

transfers genes between organisms

what is gene therapy

scientist are researching genetic modification treatments for inherited diseases caused by faulty genes - known as gene therapy. Where inserting people with disease with healthy gene but this is difficult as the faulty gene would be in all of the persons cells meaning the new gene would have to be transferred into every cell in the body (however could try transferring gene at early stage of development)

what are some things that people might want genetic engineering

sheep - drugs in their milk is extracted and used to treat disease

bacteria- produces hormone insulin which can treat diabetes

crops- size+ quality of fruit, resistant to diseases, insects, herbicides

cons of genetic engineering

don’t know for certain how genetically modified plants might affect our health, chance might make it into the wild where it may outcompete local plates and change ecosystems, reducing biodiversity

pros of genetic engineering

easily make crops with desirable characteristics like more edible crops/being resistant to disease, increase yield, more food for less money, can produce special nutrients e.g. golden rice helps reduce blindness, can be grown without problems

what is the process of genetic engineering

1-find the gene u want , cut section of DNA out using restriction enzyme to isolate it

2-insert gene into a vector (which could be a virus or a bacterial plasmid) to insert use a enzyme called Lysozyme to cut plasmid and insert the useful gene

3-ligase is used to join plasmid and DNA back together

4-introduce this vector to whatever organism you want to have the gene and it will start to multiply/ produce the protein that the gene codes for

why is the human genome/genetic screening important

1. It helps us understand how genetic diseases work so preventative steps can be taken. People can get screened to detect health risks early and start treatment sooner.

2. It aids the diagnosis and treatment of inherited disorders by letting us quickly identify faulty genes. New personalised drugs and therapies can be tailored to a patient's specific genetic makeup (this is sometimes called personalised medicine).

drawbacks of genetic screening

1. Learning about their genetic risks can cause stress and mental health issues for some people.

2. Genetic discrimination may lead to unfair treatment in jobs and insurance for those with certain gene variants. Strict regulations are needed to prevent gene-based bias.

3. There are concerns about the misuse of genetic data by employers and insurers, emphasising the need for privacy protections.

what is antibiotic resistance

group of drugs that kill bacteria main one is penicillin

how does antibiotic resistance happen

imagine u had a colony of bacteria inside u giving u a sore throat and headache and u go to the doctors and they give u antibiotics. This hopes that the antibiotics will come into contact with the bacteria and kill them- However bacteria sometimes develop random mutations in their DNA which can change their characteristics which can result in the bacteria become less effected by the antibiotics. Even though the antibiotic kills most of the bacteria the more resistant bacteria survive. As bacteria can replicate so quickly they form a new colony which all have gene for antibiotic resistant — this is called an antibiotic resistant strain, because you are still effected by the bacteria it means you can pass the antibiotic resistant and so will need a different antibiotic to kill the bacteria in which most people this should work but sometimes some of the bacteria will also become resistant to that bacteria to

what is a superbug

bacteria that are resistant to loads of types of antibiotics

give an example of a superbug

MSRA

Why is antibiotic resistance such a problem

because we use so many antibiotics, resistance is bound to arise

what are ways we are increasing chances of increasing antibiotic resistance

-doctors often give out antibiotics in cases that wont actually help such as when someone has a viral illness (antibiotics cants kill) or non serious cases

-lots of bacteria is given to animals - farmers put antibiotics in the food of healthy animals to prevent them getting ill and to grow faster meaning that they produce lots of antibiotic resistant

-people not taking full course/length of antibiotic prescription

who is Carl Linnaeus

a man who proposed the classification system in the 1700s

define the classification system

groups species/living organisms together according to their characteristics and bone structures

what was classification known as

The Linnaean system

in this system living things are divided into what?

Kingdoms which are the subdivided into smaller groups

what are the groups / order

Kingdom, Phylum, class, order, family, genus, species

what is a good acronym to remember this

King Phillip Comes Over For Great Sex

what is the Binomial naming system

every organisms is given its own two part name first refers to genus and second refers to its species

what is the genus

genus that the organisms belongs to- gives information about organisms ancestry

In humans what is the Binomial system known as

Homo (genus) Sapiens (species)

who is Carl Woese

He came up with the three Domain system

why did Carl Woese produce this

due to improvement in microscopes allowing us to see internal structures of different species as their biochemical processes developed and due to evidence from new techniques that could analyse RSA sequences where he found some species where less related than we thought