Topic 3- Genetics Flashcards by Artemis Buxton

Advantages of asexual reproduction?

-Saves time and energy finding a mate
-Population can increase rapidly when environment is favourable

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Advantages of sexual reproduction?

-Genetic variation
-Selective breeding
-Natural selection

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What does meosis produce?

-Produces 4 haploid gametes
-Genetically different to eachother

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How does meosis work?

1)Chromosomes make identical copies of themselves
2)Similar copies pair up
3)Swap sections
4)Divide as two chromatids
5) Divde again as one chromatid

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What happens in fertilsation?

-Gametes fuse to form one diploid cell

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What is DNA made of?

-DNA is a polymer
-Each monomer/ nucleotidee is made of a sugar, phosphate and a base
-Attached to a sugar phosphate backbone

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What are the bases DNA has?

-Adenine
-Thymine
-Guanine
-Cytosin

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What is DNA compared to RNA?

-DNA is double helix (two strands)
-RNA has no T base only U

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What is the genome?

Entire genetic code of an organism

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What is a gene?

A part of a chromosome that codes for a specific protieen

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What acid is DNA?

nucleic acid

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How to extract DNA from fruit?

1) Mash with salt water —> Break cells apart + membranes (salt helps clump later) + heat in water bath
2) Seive for soup—-> (no clumps)
3) Add detergent—-> Breaks membrane + nucleus membrane
4) Add protease (protien enzyme)—-> breaks protien that DNA binds to (DNA now strings)
5) Slowly pour thin layer of ice cold ethanol—> DNA insoluable in ehtanol + less dense than water (solidifies + clumbs due to salt as a layer underneath the ethanol)

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How are protiens made?

-Protien synthesis

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Why are there different protiens?

-Different order of nucleotide bases
-Cuase different tRNA molecule to bring a different amino acid

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What are the two steps of protien synthesis?

-Transcription
-Translation

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Where does transcription happen?

In the nucleus

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Why does transcription occur in the nucleus?

DNA too big to leave nucleus

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What happens in transcription?

1) RNA polymerase binds to the non coding section of DNA (located at the start of a gene)
2) Helicase enzyme breaks hydrogen bonds between double helix- seperates two strands of DNA
3) RNA polymerase moves along the coding section and produces a complementory mRNA strand.

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What happens in translation?

1) mRNA attaches to a ribisome
2) Ribisome reads mRNA codons (3 nucleotides)
3) Allows correct tRNA molecule to collect its amino acid
4) Amino acid form a plolypetptide chain
5) When finished, polypetpide chain folds into a unique 3D protien

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Why do mutations normally have no/little affect?

-Many different tRNA find the same amino acid

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What does genetic variation in the non-coding/coding region of DNA do?

Changes phenotype

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How does genetic variation in the non-coding region affect phenotype?

-Changes how much RNA polymerase can bind to it
-If less, less mRNA is produced
-Could stop entire gene being read

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How does genetic variation in the coding region affect phenotype?

-Alters sequence of bases
-Changes codon read
-Changes which amino acid is brought

What types of mutation are there?

Substitution- One nucleotide is changed for another (may not affect protien)
Insertion- A nucletodie is added —> Affects all codons read after it
Deletion- A nucleotide is taken away —->Affects all codons read after it

Who discovered principls of inheritence?

Dr Mendel

What did Dr mendel do before his experiments?

-Studied maths + natural history in Vienna -Monostery gardens ----> he observed | People believed in blending theory

What experiment did Mendel do?

-Smooth vs Wrinkled peas -Green vs Yellow peas

Mendel experiment results, generation 1 and 2?

1) All smooth (dominant) 2) 1/4 wrinkled (recessives

What did Mendels experiment prove?

-Children looked like parents becuase they inherited "heriditary units" -One form both parents -One was dominant (visible), one was recessive

Why was Mendels work not recognised in 1866?

-No knowledge of genes/ chromsomes till much later

How do alleles control characteristics?

-Different forms of the same gene -Codes for different characterstics

What is a **chromosome**?

-Long strand of **DNA** found in the nucleus

What is a **gene**?

-**Section** of **DNA** that codes for a protien (some characteristics are coded by more than on gene)

What is a **allele**?

-Different versions of a gene -One from each parent

What is a **dominant/ recessive** allele?

-**Dominent** needs one allele to be expressed -**Recessive** = both have to be in order to be expressed

What is a **homozygous/ heterozygous**?

-Homozygous--> Both alleles are the same -Heterozygous---> Alleles are different (one dominent one recessive)

What is the **genome**?

Organisms entire genetic material

What is a **genotype**?

-The combination of alleles

What is the **phenotype**?

-The expressed/ visible characteristics

What is a **gamete**?

-Haploid sex cell -Egg cell/ sperm

What is a **zygote**?

-Straight after fertilisation -Diploid cell fused from two gametes

What graph shows propability of child's genotype from parents alleles?

-Punnett square

What graph shows different characteristics in a family?

Famly pedegrees

Why is fertilisation chance of boy/girl 50%?

-Mother has XX -Father had XY (Y is dominent) (sperm carries either X or Y)

What does autosmal reccesive means?

-Needs both alleles to have mutated gene

What is codominance?

-More than one allele determines characteristics -More than one allele will be dominant -Present in the same position (or locus)

Example of codominance?

-Blood ABO groups -Two expressed at the same locus -A and B are dominant -O is recessive e.g -A+A=A -A+B=AB -B+O=B -O+O=O

What are sex-linked disorders inherited?

-Normally found on the X chromosome

On a punnet square, how do we present an affected X chromosome?

X= normal X^D= Affected

Why are males more likely to develope sex linked diseases?

-Women = two X -Men = one X -Women have higher chance of one of their X's not having the mutation, therefore aree carries but not affected -Males only need one X to be affected as the Y cannot compensate

Main examples of sex-linked diseases?

-Colour blindess -Haemophelia

Example of Phenotype are a result of mutliple genes? | Mostly the result of multiple genes

-16 genes -eye colour

What changes phenotype?

-Genetic variation- random mutations and sexual reproduction cuases new combinattion -Environmental factors- No change in DNA, malnutrition (could still have a tall genotype)

Do most genetic mutations effect phenotype?

-No, most don't or only have a small affect -Very rarely a small mutation will drastically change phenotype

Why does everyone look different?

-Populations have extensive genetic variation -These arose through mutations

What were the outcomes of the Human Genome project?

-Completly mapped human DNA (20K-25K genes) -Improved understanding of genes linked to diseases e.g cystic fibrosis

What can we use the human genome project for?

-Finding genetic **diseases** e.g sickle cell anemia and cystic fibrosis + early diagnosis -Personalised treatement--> works better for different genetic make-up -Gene therapy- replacing fualty genes