B1 whole revision

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B1

– You and your genes

B1.1

What are genes and how do they affect the way organisms develop

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Inherited

characteristics are passed on by genes e.g. eye colour

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Environmental

characteristics depend on the kind of environment you live in and how its conditions

can change your characteristics e.g. skin tan or how it influences you to adapt

within your chosen lifestyle e.g. tattoos or piercing

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A

cell has a nucleus, which contains genetic information and is in charge of the

activities within the cell.

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The

nucleus has single-coiled molecules of chromosomes which are made up of a

chemical called DNA.

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The

DNA is a molecule and a section of the molecule consists of our genes.

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Genes

determine how we develop and give instructions for a particular characteristic(s).

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Genes

give instructions to make proteins which are important chemicals for our cells

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There

are two types of proteins

1.

Structural

proteins – build the body and found in tendons e.g. collagen

2.

Functional

proteins – contribute to the chemical reactions of the body e.g. enzymes like

amylase

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Some

characteristics rely on several genes working together e.g. eye colour

B1.2 Why can people look like their parents,

brothers and sisters, but not identical to them?

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Identical

twins form when a fertilised egg splits into two to develop two genetically

identical babies

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Differenced

between them are due to the environment

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We

call genetically identical organisms clones

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In

plants clones are produced through asexual reproduction, where only one

organism is required to produce offspring (mainly in plants).

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Chromosomes

come in pairs, carrying the same genes in the same place – this means your

genes also come in pairs

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Every

human cell has 23 pairs of chromosomes – the 23rd pair being the sex

cell

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Number

of chromosomes:

1.

Male

body cell – 46

2.

Sperm

cell – 23

3.

Female

body cell – 46

4.

Egg

cell – 23

5.

Fertilised

egg – 23 pairs aka 46

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A

fertilised human egg cell has 23 pairs of chromosomes

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Male

– XY

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Female

– XX

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Sperm

cell – X or Y

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Egg

cell – XX

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Hormones

are chemicals that control many processes within the cells

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An

embryo needs a Y cell to become a boy as all male body cells have an XY

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A

sperm cell determines the gender of the baby

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A

genetic diagram tells us what the chances are of us receiving a particular

characteristic

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Homozygous

are alleles that are the same

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Heterozygous

are alleles that are different

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Alleles

are different versions of genes –

they can be represented using letters

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Dominant

alleles determine the characteristic if only one of them or both of them are

present and they are represented in capital letters e.g. DD or Dd

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Recessive

alleles determine the characteristic only if both of them are present and they

are represented in small letters e.g. dd

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Individuals

usually have two alleles for each gene

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Genes

come from both parents to produce variations in the offspring.

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Genotype refers to the genetic description of

the offspring

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Phenotype

refers to the physical appearance of the offspring

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Offspring

have similarities to their parents due to a combination of maternal and

paternal alleles in the fertilised egg

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Brothers

and sisters can differ from each because they inherit different combination of

maternal and paternal alleles

B1.3 How can and should genetic information be

used? How can we use our knowledge of genes to prevent disease?

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Huntington’s

disease is inherited if both alleles are dominant and either of the parents are

carriers

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Symptoms

include; memory loss, behavioral issues, problems controlling muscles,

twitching etc.

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Cystic

fibrosis is a genetic disorder that is inherited if two recessive alleles are

present with either one of the parents being a carrier

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Symptoms

include; thick, sticky mucus that prevent enough oxygen getting to lungs, thus

resulting in breathing problems and it also stops enzymes getting to the gut.

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So

this can result in digestive problems and there’s a problems with gaining

weight.

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Some

people are carriers of such genetic disorders due to family history of

inheriting the gene for the genetic disease

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Ethics

are beliefs based on religion or morals which tell us what is wrong or right

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False

positive is when the result comes back positive when in reality it is negative

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False

negative is when the result comes back negative when in reality it is positive

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Genetic

testing is when people are tested to check for any genetic disorders because

they have a family history of the condition

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Genetic

screening is when people are screened for a particular condition but don’t have

a family history of the condition

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In

vitro fertilisation is when eggs are removed from ovaries and so is the sperm

and reproduction is taken place in labs or glass to produce a baby

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Pre-implantation

genetic disease identify embryos at risk

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Stem

cells are undifferentiated, biological cells that can be differentiated into a

cell or tissue that has been damaged and needs replacing.