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EdExcel GCSE - Biology - Topic 3 - Genetics
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- 1What is Meiosis?A method of cell division, which creates 4 genetically different haploid cells
- 2Where does Meiosis take place?Testes / Ovaries
- 3How many times do cells in Meiosis divide?2
- 4What is a gene?A section of DNA that often contains instructions for a specific protein
- 5What is a genome?All of the DNA in an organism. Each body cell contains a copy of the genome
- 6What is a polymer?A long chain molecule created by joining up many smaller molecules (monomers) together
- 7What is a protein?A polymer made up of amino acids
- 8What is a zygote?A fertilised egg cell
- 9What does diploid mean?Cell contains 2 sets of chromosomes (46 in humans)
- 10What does haploid mean?Cell contains 1 set of chromosomes (23 in humans)
- 11What is DNA's structure?Double-helix (2 strands that are joined together and twisted around each other)
- 12What are the strands of DNA held together by?Pairs of bases
- 13What are the 4 bases in DNA?Adenine, Thymine, Guanine, Cytosine
- 14What does Adenine pair with?Thymine
- 15What does Guanine pair with?Cytosine
- 16Fill in the blank: Each base in DNA is attached to a _____ called __________, and each sugar is attached to a __________ _________. This grouping is called a ________sugar
deoxyribose
phosphate group
nucleotide - 17What holds the base pairs together in DNA?Hydrogen Bonds
- 18What are the two stages of protein synthesis?Transcription and Translation
- 19What is RNA?Single stranded molecule similar to DNA, except uses Uracil instead of Thymine
- 20What happens in transcription?Produces mRNA to form DNA. mRNA is small enough to leave the nucleus and go to the ribosome.
1. DNA in the nucleus unwinds due to the RNA polymerase enzyme, which binds to a non coding region
2. mRNA nucleotides pair up to the template strand with their complementary base pairs
3. Hydrogen bonds break between the mRNA nucleotides and the DNA. The mRNA is now a single strand with complementary base pairs to DNA - 21What happens in translation?Occurs in the cytoplasm, with the help of ribosomes.
tRNA molecules have an amino acid and anti-codon on each end, which are complementary to a codon (3 bases in DNA)
Each anti-codon is complementary to a codon on DNA
tRNA binds temporarily to the mRNA, which brings each amino acid on the molecule closer together
Peptide bonds are formed between amino acid, making a polypeptide chain form
Process continues until a "stop" codon is reached - 22ok that was a lot of stuff, unless you're viewing this in a different order. so go take a small break or go over it or something idkdrink some water
- 23What is a phenotype?The physical characteristics determined by alleles
- 24What are alleles?Different forms of a gene
- 25What is a genotype?The combination of alleles that an organism has
- 26Hip hip hooray...for DNA!
- 27Summarise what Gregor Mendel (pea guy) did to study phenotypes?Cross-bred different plants with different characteristics, and determined if it would be recessive or dominant.
- 28What is a recessive allele?An allele that doesn't change the phenotype (physical characteristic) but could be passed on
- 29What is a dominant allele?An allele that always affects the phenotype
- 30What is a homozygous gene?When both alleles for a gene are the same in an organism
i- i mean gey - 31What is a heterozygous gene?When both alleles for a gene are different in an organism
- 32In punnett squares, what do capital and lowercase letters mean?CAPITAL IS DOMINANT
lowercase is recessive - 33What is a co-dominant allele?An allele that are both expressed in the phenotype
- 34What is an example of co-dominant alleles?Blood Types (specifically A and B alleles making AB blood)
- 35What is a mutation?A change in a gene that creates a new allele
- 36When do mutations often occur?In cell division
- 37Fill in the blanks: ________ can cause mutations in genes. __ __________ from the sun can cause mutations leading to ______ ______Radiation
UV radiation
skin cancer - 38What is the human genome project?A collaborative effort to sequence the whole human genome
- 39Why was the human genome project useful?Allowed for diagnosis of genetic disorders and "Personalised Medicine"
- 40What is genetic variation?Variation caused by the different alleles inherited during the saucy times
- 41What is environmental variation?Variation caused by the surroundings
- 42What are acquired characteristics?Characteristics that are changed by the environment during an individual's life (such as an injury that causes permanent effects)
- 43What is continuous variation?Variation where the characteristic can have a range of values (eg. Height and Weight)
- 44What is discontinuous variation?Variation where the characteristic fits into certain categories (eg. Hair Colour and Blood Type)
- 45What shape curve does continuous variation form when plotted?A bell-shaped curve (normal distribution)
- 46What is Meiosis?> Method of cell division
> Creates 4 genetically different haploid cells
> Takes place in the testes / ovaries
> Cells divide twice - 47What happens in Meiosis?> Cell duplicates DNA so there's enough for each new cell
First division:
- Chromosomes line up in pairs in the centre of the cell
- Pairs are pulled apart
- Each new cell will only have one copy of each chromosome
- Each new cell will have a mixture of the chromosomes
- This creates genetic variation in the offspring
Second Division:
- Chromosomes line up again
- Chromosomes are pulled apart into chromatids
- Creates four haploid daughter cells
- These are gametes
- Gametes are all genetically different - 48What is a Gene?A section of DNA that often contains instructions for a specific protein
- 49What is a Genome?> All of the DNA in an organism
> Each body cell contains a copy of the genome - 50What is DNA's Structure?Double-helix (2 strands that are joined together and twisted around each other)
- 51What are the 4 bases in DNA and what do they Pair With?Adenine, Thymine, Guanine, Cytosine
A = T
G ≡ C - 52Fill in the blank: Each base in DNA is attached to a _____ called __________, and each sugar is attached to a __________ _________. This grouping is called a ________Each base in DNA is attached to a SUGAR called DEOXYRIBOSE, and each sugar is attached to a PHOSPHATE GROUP. This grouping is called a NUCLEOTIDE
- 53What holds the Base Pairs together in DNA?Hydrogen Bonds
- 54What are the two Stages of Protein Synthesis?1. Transcription
2. Translation