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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.