Biology - Unit 2b - Inheritance, Variation and Evolution

What is a single chromosome made of?

One long coiled up molecule of DNA

How are gene’s arranged on the chromosome?

In a linear arrangement

What do gene’s determine?

characteristic development

What are DNA backbones made of?

Long chains of sugar and phosphate molecules

What are the 4 bases in DNA?

Adenine, Thymine, Cytosine, Guanine

Which bases pair up according to the complementry base pairing?

A - T

C - G

What’s the name for the type of base pairing?

Complementry base pairing

How are the complemenrty base pairs joined together?

Weak hydrogen bonds

How do gene’s work?

It’s the order of bases in a gene that decides the order of amino acids in a protein. Every three bases (triplet) codes for one amino acid

How can protiens be synthesised if DNA is too big to move out of the nucleus?

A molecule is used to relay the triplet code from the DNA to the cyctoplasm for protiens to be synthesised

What is Mitosis?

A cell reproduces itself by dividing to form two identical offsprings

Why would a cell use mitosis?

Growth, Replace, Repair

Describe how mitosis happens?

• DNA strands form into chromosomes then duplicate

• Line up in cell center and arms of chromosomes are pulled apart by cell fibres to either pole

• Membranes form around each set - becomes new nuclei

• Cytokinesis occurs

How is cancer connected to Mitosis?

If the gene that decides the rate of cell division changes, it may start to divide uncontrollably. Leads to loads of abnormal cells called a tumour. If it invades/destroys surrounding tissue, it’s called cancer

What is Meiosis for?

Meiosis produces gametes

What makes gametes different?

They only have one copy of each chromosome (23 chromosomes)

Describe how meiosis happens

• DNA strands form into their chromosomes then duplicate themselves

• Line up at the centre in their pairs (left and right is random)

• Line is split into two and cell divides

• Line up again in centre, then arms are pulled apart by cell fibres

What is differentiation?

Stem cells will divide by mitosis and then differentiate into specialised cells

What are embryonic stem cells?

They can differentiate into any kind of cell

What are adult stem cells and give an example?

Not as versatile as embryonic stem cells. Only used to replace or repair cells e.g. cells in bone marrow make new blood cells

How can stem cells cure diseases?

Stem cells can be extracted from embryos and will be stimulated to differentiate into specialised cells under certain conditions. We can use these cells to replace damaged ones in a patient

What are 3 benefits to using your own cells to treat some diseases?

• No need to wait for donor

• No need for tissue typing

• No chance of rejection

Give 2 ways people are against stem cell research?

• They belive every embryo is a potential life

• They believe scientists should focus on finding other sources of stem cells

Every DNA is unique, but what are the exceptions?

Identical twins and clones

What is Genetic Profiling?

A way of cutting up DNA into small sections and then seperating them

How does Genetic Profiling work?

• Extract DNA from cell

• Cut up DNA into different sized fragments

• Separate fragments using gel electrophoresis

• Suspend in alkaline gel with electrical current passing through

• Smaller fragments will travel faster and therefore further down the gel - because DNA becomes negatively charged when in gel, so will travel towards positive end of the gel (+ve)

What are 5 ways we use Genetic profiling?

• Paternity tests

• Species classification

• Forensic Science

• Diagnoses of dieases

• Finding a patients risk rate for a disease

Why do some people think a national gentic database is bad idea?

They worry insurance companies would refuse people who have genes associated with a gene

What’s it called when characteristics are controlled by a single cell?

Single gene inheritance

Whats a genotype?

Set of alleles an individual has that determines a characteristic

What’s a Allele?

Different form of the gene

What’s a Phenotype

The appearance of an organism as a result from its genotype

What is Heterozygous

Two different alleles

What is homozygous?

Two of the same alleles

What is filial?

A group of related offspring

What does F1 mean?

First filial generation

What is F2?

Second filial generation

What is Selfing?

Self-fertilisation - pollen and eggs from the same plant are crossed

What is Genetic Modification?

Artifically transfering a desired characteristic from one organism to another

How does Genetic Modifiaction work?

Gene is cut from genome using enzymes and put into vector. Then, vector is introduced to targeted organism which inserts gene into the cell(s)

What are 3 ways we can use Genetic Modification?

Crops - resistant to pests, chemical pesticides and deficiency diseases

Modify human bacteria to produce insulin

Transfer useful genes from humans to animals

What are 4 risks to using Genetic Modification?

“Superseeds”

Bioaccumulation

Biodiversity

Unforeseen problems for the future

What are 2 ethical issues with Genetic Modification?

‘Genetic underclass’

Humans benifit but animals suffer

What is Genetic Variation?

Differences in the same species due to the random variation of genes inherited by the mother and father

What is Enviromental Variation and give an example?

Differences between the same species becuase they’ve been modified due to their enviroment

e.g. a plant grown in the sun will have green leaves however the same species of plant that grew in darkness has yellow leaves due to less chlorophyll production

What is Continuous Variation?

Species charcteristics vary within a range as there are no distinct categories

These characteristics will have been developed by more than one gene or could have been effected by the enviroment

The graoh will show a bell-shaped curve

What is Discontinuos Variation?

Species characteristics have distinct categories where an individual will fall into only one category

Only influenced by one gene and not effected by their enviroment

What is Sexual Reproduction?

Fusion of both female and male gametes. This means there will be a variation of both the mother and father gene’s

What is Asexual Reproduction?

Only one parent, no fusion, so offspring’s are identical

Explain why there is variation in the offspring of sexual reproduction?

There are two parents so the offspring will be a misture of both their genes. This mixture of DNA produces variation

What is a mutation and how can its rate be increase?

Random change in organisms DNA that can be increased by exposure to ionising radiation

What is cystic Fibrosis?

A mutation that causes a protien to stop working. This protien controls the movement of salt and water in and of the cells. This causes thick and sticky mucus in the in the lungs and the digestive system which makes it really hard to breathe and digest food

What is Natural Selection/evolution?

Process by which organisms that are better adapted to their enviroment tend to survive and reproduce, leading them to pass on their advantageous allele to furture generations. This leads to gradual evoltion of species over time

How do species become extinct?

If the enviroment changes too quickly then the process of natural selection cant adapt to rapid enviromental changes

What are 3 ways we know evolution is still happening?

• Antibiotic Resistance

• Warfarin Resistance

• Pesticide Resistance

What is the Human Genome Project?

Scientists were able to map out around 20,500 genes in a human genome

What are 3 drawbacks to the Human Genome Project?

Increased stress - Person may worry all the time about when their susceptible disease could develop

Discrimination from employers and insurers if someone has a genetic likelihood of a serious disease

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