Genetics - topic 3 (pg 20-28) paper 1 Flashcards Preview

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1

meiosis

produces four daughter cells each with half the number of chromosomes
only in gamete producing cells, producing genetically different haploid gametes

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haploid

one set of chromosomes (me-1-osis)

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stages of meiosis

the parent cell is a diplod cell (two pairs of chromosomes --> parent cell dividesin two then two again
- before the parent cell divides, each chromosome is copied
- each daughter cell gets a copy of one chromosome form each pair
- each daughter cell has one different haploid set of chromosomes

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DNA

Deoxyribonucleic acid - genetic material found in the chromosomes in the nucleus of cells

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gene

short piece of DNA that codes for a specific protein, codes for a characteristic

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structure of DNA

molecule formed from two strands twisted together in a double helix

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DNA bases

A(adenine) T(thymine)
C(cytosine) G(guanine)

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what hols DNA strand together

weak hydrogen bonds

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DNA structure

DNA is a polymer made of monomers called nucleotides joined together

Phosphate (circle)
deoxyribose sugar (pentagon) Base (square)

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when gametes fuse they form a

diploid zygote

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allele

different versions of the same gene

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chromosomes of the same pair have

the same genes in the same order

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heterozygous

different alleles of the same gene

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homozygous

same alleles on both chromosomes

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genotype

shows the alleles in each individual - punnet squares

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phenotype

the characteristics that are produced - punnet squares

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dominant

will show when one allele is present in the genotype

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recessive

will only show when two alleles are present in the genotype

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pedigree analysis

used to study inheritance of dominant and recessive alleles
predict the chance of someone inheriting a specific allele

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carriers

have one copy of a faulty allele

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genotype XX

female chromosomes

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genotype XY

male chromosomes

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at fertilisation there is an equal chance of

producing a male or a female

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variation factors can be

genetic and environmental

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phenotypic features

hair colour, eye colour
caused by many genes

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genetic variation

hair colour
eye colour

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environmental variation

scars
ability to ride a bike

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genetic and environmental variation

weight
skin colour

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mutation is created

when subsequent bases in a gene is changed

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mutations however

- most genetic mutations have no effect on phenotype
- some have a small effect
- a single mutation rarely, significantly affects the phenotype

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a mutation may cause

- a large change in protein produced
- a small change
- no change

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mutation in non coding DNA can

increase or decrease ability of RNA polymerase to bind to DNA

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The Human Genome Project

collaboration between scientists to decode the human genome (order of bases on all human chromosomes)
- completed quickly due to number of scientists working at the same time
- published in 2003
- used for new medicines

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advantages of the human genome project

- alerting people they are at risk of particular diseases
- distinguishing between differences in diseases like leukaemia, some drugs are beneficial for different forms
- allowing doctor to 'tailor treatments' for some diseases to the individual

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disadvantages of the human genome project

people who were at risk of certain disease like cancer could have claimed more life insurance
- may not be useful to tell someone the risk of a condition with no cure currently