Biology - B1 You and your genes

OCR GCSE

Prokaryotic

Small simple cells including bacteria

Eukaryotic

Complex cells including animal and plant cells

Nucleus

A subcellular structure which contains DNA arranged into chromosomes

Cytoplasm

A gel-like substance within cells where all the reactions happen. Also contains enzymes.

Partially permeable cell membrane

Holds the cell together and controls what goes in and out.

Mitochondria

Contains enzymes needed to control aerobic respiration within the cell

Ribosomes

A subcellular structure that is involved with protein synthesis

Cell wall

Supports the cell and is made of cellulose. Only found in plant cells

Vacuole

A subcellular structure that contains cell sap. Only found in plant cells.

Chloroplasts

A subcellular structure where photosynthesis occurs. Contain chlorophyll.

Plasmids

Subcellular structures that are small loops of extra DNA which typically carry traits such as drug resistance. Only in Prokaryotic cells.

Light microscope

These pass light through a specimen to magnify and identify the specimen’s features (usually subcellular structures).

Stage

Where the specimen is placed on a light microscope.

Objective lens

The part that magnifies the specimen on a light microscope.

Coarse adjustment knob

Moves the stage quickly to gain focus on a light microscope.

Fine adjustment knob

Slowly moves the stage to gain focus on a light microscope.

Genome

The entire genetic material of an organism

Chromosome

A long molecule of DNA coiled up. Usually in pairs. Humans have 23 pairs.

DNA

A polymer made up of nucleotides in a double helix.

Gene

A short length of DNA that codes for specific amino acids to make a specific protein.

Alleles

Genetic variants or different versions of a gene created when DNA mutates

Genotype

The combinations of alleles the organisms have

Phenotype

The characteristics that an organisms presents with. It’s effected by the genotype and the organism’s environment.

Nucleotide

The monomer that makes up DNA. Made up of a base, a sugar and a phosphate group. Only the base varies.

Base of nucleotides

There are four different ones: Adenine(A), Thymine(T), Cytosine(C) and Guanine(G)

Complementary base pairing

Adenine always pairs with Thymine and Cytosine always pairs with Guanine.

Amino Acids

Coded for by triplets (three nucleotide bases) to make specific proteins.

mRNA

Like DNA but single stranded and uses Uracil instead on Thymine. Responsible for protein synthesis.

Protein Synthesis

The DNA in the nucleus 'unzips' and mRNA is created as complementary to the DNA strand. The mRNA then moves out of the nucleus and attaches to a ribosome. The Ribosome then sequences the correct amino acids based on the mRNA and codes for the protein.

Insertion

A type of DNA mutation where a new base is inserted and changes the way that triplets are read

Deletion

A type of DNA where a base is removed from the sequence and changes the way triplets are read.

Substitution

A type of DNA mutation where a random base is changed to another. It doesn’t always effect the amino acids because they can be coded for by more than one triplet.

Cystic Fibrosis

caused by the deletion of three bases, this disorder produces a protein that doesn’t control the movement of salt of water out of cells like it should causing excess mucus production.

Mutation

When a base sequence is changed in someway. It usually has no or little effect on coding DNA and the organisms phenotype. It can cause non-coding DNA to wrongly control the expression of a protein and therefore effect the phenotype.

Gametes

Reproductive cells which only have one copy of each gene. This means that when the male and female cell combine, the offspring has a pair of each gene (2 alleles).

Dominant Allele

A trait that is present in offspring even if heterozygous (i.e. Bb)

Recessive allele

A trait that is only present if homozygous (i.e. bb)

Homozygous

Two alleles that are the same like BB or bb

Heterozygous

Two alleles that are different like Bb

Punnet square

Sex chromosomes

Men have XY chromosomes and women have XX chromosomes

Family tree

Mendel

An Austrian monk who studied the transfer of characteristics from a parent to it’s offspring in pea plants. The base of modern genetics

Genetic testing

This can find certain genetic variants in children so that treatment can start early or if a person were to have a variant that caused a treatment to have no effect this would allow the doctor to find an alternative early in the treatment process.

drawbacks to knowing genetic information

Employers may discriminate if they know that you’re more likely to get a disease. Unnecessary stress or health paranoia if you know that you’re susceptible to a disease.

Parent testing

This can allow doctors to find if a parent is even just a carrier of a disease to help with family planning

Embryo testing

Similar to IVF, eggs can be extracted and fertilized then tested and those without the disease can then be implanted.

Foetus testing

Testing some DNA from the Amniotic fluid can determine if the child has a genetic disease but this has a chance of miscarriage.

Cons of embryonic/foetus testing

It is not 100% perfect and it could cause accidental termination of a pregnancy.

Genetic engineering

The transfer of a desired gene from one genome to another genome.

Genetic engineering in agriculture and medicine

Genetic engineering can be used in place of herbicides to create a weed resistant plant( runs the risk of creating a super weed in the process) or to make medicine such as insulin by adding useful genes toa cow or sheep then extracting the useful proteins through it’s risk (could cause the animal to become ill or diseased).