You and Your Genes

What are prokaryotes?

An organsim that lacks a nuclus because of its absence of internal membranes. Cells of bacteria are called prokaryotic cells.

What are eukaryotes?

Eukaryotas are cells that have a nucleus, and organelles that have different functions(like the mitochondria, which produces energy).
Eukaryotas can include simple organisms like protozoa. Human cells are Eukaryotes! Cells of animals, plants and fungi are called eukaryotic cells.

Cytoplasm

Where enzymes and other proteins are made. Location of reactions in anaerobic respiration.

Nucleus

Contains DNA which carries the genetic code for making enzymes and other proteins used in chemical reactions such as photosynthesis and respiration.

Cell membrane

Allows gases and water to diffuse freely into and out of the cell. Controls the transport of other molecules.

Mitochondrian /dria

Contains enzymes for the reactions in aerobic respiration (in animals, plants and yeast).

Ribosome

Where amino acids are joined together to make a protein.

What are the additional structures do plant cells have which animal cells don't? Describe.

Chloroplasts- Contains the green pigment, chlorophyll, which absorbs light for photosynthesis, and the enzymes needed for photosynthesis.

Cell wall- Made from cellulose fibres. Strengthens the cell and supports the plant.

Vacuole- Filled with cell sap to help support the cell.

Chitin (yeast cells)

In cell walls, helps strengthen the cell.

What are the differences and similarities between the outer layers of both eukaryotes and prokaryotes?

Both contain cytoplasm and ribosomes.
However, eukaryotes have cell organelles like mitochondria and chloroplasts.

Describe root hair cells.

They absorb water and minerals.
A long thin 'hair' extends from each cell into the soil increasing the root's surface area. Each root has many thousands of root hairs, which can make the root look furry.

Describe xylem cells

They transport water and minerals up the stem to leaves and flowers.
Dead cells are joined end to end to form a continuous tube. They have no cytoplasm. Their walls contain lignin for strengthening.

Describe phloem cells

They transport sugars, amino acids, other substances both up and down the stem to leaves, flowers and roots.
Made of tube-like living cells joined end to end. They do have cytoplasm. This means that the cells are living.

What is a genome?

The entire genetic material in an organism.

Describe the structure of DNA

a polymer of nucleotides joined together as two strands in a double helix.

What are nucleotides made of?

sugar, phosphate group, nitrogen base

How many bases do nucleotides have?

There are four nucleotides, or bases, in DNA: adenine (A), cytosine (C), guanine (G), and thymine (T).

How do the bases pair together

A, T, C, G

What do human genomes allow us to do?

-search for genes linked to different types of disease
-understand inherited disorders and their treatment
-trace human migration patterns from the past

Phenylketonuria (PKU)

inherited disorder in which the infant lacks a liver enzyme

Allelle

Different forms of a gene

Genotype

the alleles for the genes that someone carries

Phenotype

The phenotype of an organism describes its features. It is the result of the information in its DNA (genotype + gene expression) and any interaction with the environment. Physical traits.

Genetic causes of variation

-They inherit their features from each parent's DNA.
-Every sperm and egg cell contains half of the genetic information needed for an individual.
-sperm and eggs contain half the normal number chromosomes. When the chromosomes fuse during fertilisation, a new cell is formed, which is known as a zygote.
-It has all the genetic information needed for an individual and has the full number of chromosomes.

Examples of genetic variation in humans
- blood group
- skin colour
- natural eye colour

Environmental causes of variation

-Characteristics of animal and plant species can be affected by factors such as climate, diet, accidents, culture and lifestyle.
-For example, if you eat too much you will become heavier. If you eat too little you will become lighter.
-A plant in the shade of a big tree will grow taller to reach more light.

examples of features that show environmental variation include:
-scars
-language and accent
-flower colour in hydrangeas as these plants produce blue flowers in acidic soil and pink flowers in alkaline soil.

DNA

a natural polymer made of nucleotides. It forms two strands in a double helix. It carries the genetic code, which controls how an organism develops and functions. With the exception of identical twins, each person's DNA is unique.

Chromosomes

inside the cell's nucleus.
These are long, thin, threadlike structures made from molecules of DNA that store genetic information.
Chromosomes are found in the nucleus of body cells in pairs - one chromosome is inherited from the mother and one is inherited from the father.
The chromosome in each pair carries the same gene in the same location. These genes could be the same, or different variants.

Genes

a region of DNA containing the instructions for a cell that give the order of amino acids in a protein.
Some characteristics are controlled by a single gene, such as ear wax texture in humans or pea shape in peas.
Each gene might have different forms, and these are called alleles.

Nucleotides

Basic units of DNA molecule, composed of a sugar, a phosphate, and one of 4 DNA bases.

Gamete

A gamete is a sex cell.
Male and female gametes fuse during fertilisation.
In humans, the male gamete is the sperm and the female gamete is the ovum (egg cell).
Both the egg and the sperm have 23 chromosomes, which combine to make a fertilised egg (zygote) of 46 chromosomes.

dominant allele

An allele whose trait always shows up in the organism when the allele is present. They are represented as a capital letter like H for example.

recessive allele

An allele that is masked when a dominant allele is present. They are represented as a lower case letter for example h.

homozygous alleles

pair of alleles for a single gene which contain the same genetic information. For example HH or hh.

heterozygous alleles

both alleles are different, one is expressed and the other doesn't affect the organism and the allele that is expressed is dominant. For example Hh.

Inheritance of biological sex

Human body cells have 23 pairs of chromosomes in the nucleus. Twenty two pairs control most of the characteristics. Pair 23 are the sex chromosomes. They carry genes that determine an embryo's sex - whether offspring are male or female:

males have two different sex chromosomes, X Y
females have two X chromosomes, XX

Genetic screening

is when genome sequencing is carried out on large numbers of people in order to use the information to predict the likelihood of gene-related issues.

genetic sequencing

the process of determining the precise order of nucleotides within a DNA molecule

cystic fibrosis

A genetic disorder that occurs in people with two copies of a certain recessive allele; characterized by an excessive secretion of mucus and consequent vulnerability to infection; fatal if untreated. In order for a baby to be born with cystic fibrosis, both of its parents need to be carriers.

When would the first symptoms of CF be noticed?

When you're about 2 years old

Which are the effects of Cystic fibrosis

Thick mucus in the respiratory, digestive and reproductive systems

What is the cause of Huntington's disease?

degeneration of basal nuclei

What are the two ways to test a fetus to see if it's affected by the genetic condition.

There are two methods to test a fetus to find out if it is affected by a genetic condition:

amniocentesis - a sample of the amniotic fluid is removed and a genetic test done on cells in the fluid
chorionic villus sampling (CVS) - a suction tube is used to remove cells from the placenta and a genetic test done on the cells
Both procedures carry a small risk of miscarriage (estimated lower than 1%), which is an important consideration when deciding whether to be tested.

genetic engineering

also called genetic modification or GM. It involves modifying the genome of an organism by introducing a gene from another organism to result in a desired characteristic.
STEPS
1.selection of the desired characteristic

2.the gene responsible for the characteristic is 'cut out' of the chromosome

3.the gene is transferred and inserted into another organism

4.replication of the modified organism

One use of genetic engineering

Diabetes is a disorder in which the body's blood glucose levels can get too high. It can be treated by injecting insulin. The extra insulin allows the glucose to be taken up from the blood by the liver and other tissues so that blood glucose levels stay normal.

Bacterial cells have been genetically modified to produce human insulin and other substances.

Another use of genetic engineering

Current genetically modified (GM) crops include those that are resistant to insect pest attack - reducing the need for pesticides - and herbicide resistant crops that allow the use of herbicides in fields to kill weeds. Both produce increased crop yields.

Why might consumers in the UK be less in favour of golden rice?

Other sources of beta carotene or vitamin A are widely available (1) may be worried about long term effects of GM or transfer of genes from species to species (1)

What are some risks of gene technologies?

- transfer of genes from modified organisms to wild organisms
- unknown long-term effects

Process of genetic engineering

1. Isolating and replicating the required genes.
2. putting the gene(s) into a vector (e.g. a plasmid)
3. using the vector to insert the gene(s) into cells
4. selecting modified cells

How many chromosomes are there in human body cells?

46 (23 pairs)

How many chromosomes are there in gametes?

23

What are the human gametes

sperm and egg

What is special about these features - earlobe shape, curving of the thumb, tongue rolling

They are caused by a single gene

Why are identical twins not completely identical?

They have inherited the the same genes (1) but the environment causes differences like scars (1).

Which sex chromosomes do egg cells contain?

X

What sex chromosomes do males have?

one X chromosome and one Y chromosome

What are chromosomes?

Chromosomes are long, thin strings of genetic material made of DNA and proteins.