Genetics Flashcards
What produces gametes?
Meiosis
Where does meiosis happens?
In the reproductive organs; Ovaries and testes.
Explain the first division in meiosis
- The cell duplicates its DNA
- The cell divides into two
- The chromosomes line up in pair at the centre of the cell
- One chromosome in a pair comes from each parent
- The pairs are then pulled apart so each new cell has one copy of each chromosome
- Each new cell now has a mixture of the mother’s and father’s chromosomes
- This creates genetic variation
Explain the second division in meiosis
- The chromosomes line up in the centre of the cell
- The chromatids are pulled apart
- You get four haploid daughter cells
- The gametes are genetically different
What are the advantages of asexual reproduction?
- It is faster
- Only one parent is needed
- Make use of resources
What are the advantages of sexual reproduction?
- Genetic variation so easier to adapt to the environment
- not genetically identical
What are the disadvantages of asexual reproduction?
- Genetically identical so there is no genetic variation
What are the disadvantages of sexual reproduction?
- A mate is needed so it takes longer
- More time and energy
- Slower growth
What are DNA made up of?
They are polymers made up of lots of repeating units of nucleotides.
Explain the structure of DNA
- It has a double helix shape
- Has sugar-phosphate backbone
- There are four bases - adenine, thymine, cytosine and guanine
- The bases have complementary base pairing
- Adenine is complementary to Thymine
- Cytosine is complementary to Guanine
- The complementary bases are held together by weak hydrogen bonds
Where is DNA stored?
In the chromosome
Explain the structure of the chromosomes
- Long coiled up molecules of DNA
- Found in the nucleus of eukaryotic cells
Describe the practical of extracting DNA from fruit cells
- Mash strawberries an put in beaker containing detergent and salt and mix well
- Filter the mixture to get the big insoluble bits out of the cell out
- Add ice-cold alcohol to mixture
- The DNA will come out the solution as it is not soluble in cold alcohol.
- It will appear as a stringy white precipitate
How are proteins made?
By reading the code in DNA
What are proteins made of?
Amino acids
Homozygous meaning
The alleles are the same
Heterozygous meaning
The alleles are different
How are proteins made?
Made by reading the code in DNA
What are genes?
Sections in DNA that code for a certain protein.
What decides the order of the amino acids in a protein?
The order of bases in a gene.
How are amino acids coded for?
By a sequence of three bases called a base triplet. The amino acids join together to make protein following the order of the bases.
What is a mutation?
A random change in an organism’s DNA base sequence.
What are the bases used in protein synthesis?
Guanine and Cytosine pair up
Uracil and Adenine pair up
What is mRNA?
Is a polymer of nucleotide, but is shorter and single stranded
What is RNA polymerase?
Is the enzyme involved in joining RNA nucleotides to make mRNA.
Explain the stage of transcription in protein synthesis
- RNA polymerase binds to a region of non-coding DNA
- The DNA is unzipped by the enzyme helicase
- The RNA polymerase moves along one strand of the DNA
- The coding DNA in the gene is used as a template for the mRNA making.
- Base pairing is ensured between the DNA and RNA ensures that mRNA is complementary to the gene
- When done the mRNA molecules move out the nucleus pores and joins with the ribosome
Explain the stage of translation in protein synthesis
- Amino acids are brought to the ribosomes by tRNA
- The order of the base triplets matches the order of amino acids brought to the membrane
- Part of the tRNA (anticodons) is complementary to the codon for amino acids
- The amino acids are joined together by the ribosomes and this makes a polypeptide (protein)
What did Mendel do with the pea plants?
He crossed a dwarf pea plant and a tall pea plant but all their offspring’s were tall pea plants. He then bred two of these tall pea plant but two of their offspring’s were tall and one was a dwarf pea plant. This showed that the height characteristics in pea plants were determined by separately inherited passed on from each parent.
What did Mendel’s pea plant experiment show?
- Characteristics in plants are determined by hereditary units
- These units are passed on to offspring’s from both parent
- These units can be dominant or recessive
What is an allele?
2 versions of each gene present in the pair of chromosomes.
How many chromosome are in the body?
46 chromosomes which make 23 pairs
