Download File - Mr Andrews` Science Space!

Who are we?
• Write a brief 2-3 sentences to describe why
these people are important!
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Friedrich Miescher
James Watson
Francis Crick
Rosalind Franklin
Maurice Wilkins
Oswald Avery
Erwin Chargaf
What is Genetics????
DNA, Chromosomes and Genes
DNA
• Cells carry instructions in the nucleus
• These instructions are about the whole
organism ( all your features)
• These instructions are carried on a
chemical called DNA
• Deoxyribonucleic acid
• DNA is a double helix
• RNA is the messenger that takes the
information outside the nucleus to be
translated into proteins
DNA and RNA
DNA structure showing
nucleotides phosphate
backbone and H bonds
Chromosomes
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Chromosomes are lengths of DNA
Humans have 46 chromosomes
These are in homologous pairs ( 23 pairs)
Homologous chromosomes have the
instructions about the same features
• We have 2 sets of chromosomes so our
cells are called diploid ( 2n)
• 1 set from Mum and 1 set from Dad
• All your genetic material is your genome
Our Chromosomes
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We have 22 pairs of autosomes
We have 1 pair of sex chromosomes
Male = XY
Female = XX
DNA and chromosomes
chromatid
proteins
DNA
Comparisons in size
Instructions
1.
Add 25g NaCl to 80mL
dishwashing liquid to make up the volume to 1L
2.
Stir to dissolve the NaCl but try to avoid frothing
3.
Add 100mL of the NaCl solution to a cut and mashed
kiwifruit in a 250mL beaker
4.
Incubate in a water bath for 15 mins
5.
Filter the kiwifruit mixture until you get 4cm in a test tube
6.
Run ice cold Meths slowly down the side of the test tube so
that is forms a 1cm layer on top of the kiwifruit filtrate
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At the interface of the 2 layers white DNA strands will form
8.
Use a pipette or hook to extract these
9.
Put onto a microscope slide
10. Stain with Bromothymol blue
Karyotype – chromosome map
A Karyogram is
a photo of
chromosomes
A replicated
chromosome
Human Karyotype
Diagram of 1 set of chromosomes showing the sex chromosomes
Genes
• Genes are lengths of a chromosomes that have
instructions for one feature
• Genes control your features
• A chromosomes is made up of many genes
• We have about 31,000 genes
• For any one feature there are different versions
eg. brown, black, blonde for hair colour
• The different versions of a gene are called
alleles
Genes - proteins
Genes to Proteins
A triplet of
bases
codes for 1
amino acid
A protein is
made up of
a long chain
of amino
acids
Your genes
• You have alleles for each feature ( one
from each parent)
• If alleles are different usually only one
shows up
• This is called the dominant allele
• The other allele is called recessive
• Your genes are called your Genotype
• Your features are called your Phenotype
Inheritance: How genes are passed on to
offspring – genetic crosses
• When doing crosses we give genes
alphabet letters
• eg. Brown eyes - dominant B
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Blue eyes - recessive b
• Each sex cell ( sperm and egg ) have only
1 allele for each feature
• eg. B or b
• The offspring have 2 alleles
More genetics terms
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Homozygous – 2 alleles the same
eg. BB or bb
Heterozygous – 2 different alleles
eg. Bb
Mendel
• Gregor Johann Mendel is called the “father
of genetics”
• He was an Austrian monk who did lots of
experiments on peas for 12 years
• He studied how features were inherited
• He drew up crosses to predict the
offspring of known parents
• He predicted ratios of inherited features
and proposed the “laws of genetics”
wrinkled
round
Punnett
square
Pedigree analysis
• Used for looking at family histories
• Used for working out
– Genotypes
– Whether traits are dominant or recessive,
autosomal or sex-linked
– Genetic counselling
Pedigrees
Pedigree symbols
Sex-linked genes
• Some genes for features are found on one
sex chromosome and not the other
• Most of these features are found on the X
chromosome
• These are called sex-linked
• eg. Red-green colour blindness, haemophilia
Sex linked inheritance
Haemophilia
Bleeders disease
where the blood does
not clot properly
Types of genetics problems
• Punnet squares – predicting ratios of
offspring
• Pedigrees – to work out genotypes
• Test crosses – to work out if a parent is
homozygous or heterozygous for a
particular feature ( trait)
Rules for doing genetic crosses
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Assign letter to the alleles
Write the phenotype
Write the genotype
Write the gametes
Draw up a Punnett square
Work out the ratios
Answer the question
NCEA information 1.9
• 5 Biological ideas relating to genetic variation are limited to
concepts and processes connected with:
• • the continuity of life based on the inheritable nature of DNA
• • links between DNA and variation in phenotypes
• • variation in phenotypes as adaptive features.
• 6 Biological concepts and processes relating to the inheritable
nature of DNA will be selected from:
• • the roles of DNA in both carrying instructions to the next generation
and determining phenotype
• • the relationship between DNA, alleles, genes, and chromosomes
• • the way in which genotype determines phenotype
• • the way chromosomes exist as pairs so that individuals inherit two
copies of each gene.
NCEA information 1.9 continued
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7 Biological concepts and processes relating to variation in phenotype will be
selected from:
• the significance of an allele as an alternative version of a gene
• the role of mutations in forming new alleles
• the role of meiosis in generating gametes (students are not required to provide the
names of the stages of meiosis)
• the significance of sexual reproduction (in producing a new mix of alleles)
• the patterns of inheritance involving simple monohybrid inheritance showing
complete dominance, sex determination, possible genotypes, and phenotype ratios.
8 Biological concepts and processes relating to variation in phenotypes as
adaptive features will be selected from:
• inheritable and non-inheritable variations that exist within a group of living
organisms
• differing rates of survival by various members of a group may depend on their
phenotype
• the importance of variation within populations (population and species survival) in a
changing environment such as pest infestation, disease, drought, or flood
• the advantages and disadvantages of sexual reproduction.
9 The student must be familiar with the following genetic language and
conventions: gene, allele, mutation, genotype, phenotype, gamete, zygote,
dominant, recessive, homozygous, heterozygous, pure breeding, Punnett square,
and pedigree chart.
NCEA questions