B3 Genetics Flashcards
What is a gamete?
Reproductive cells e.g. sperm and egg cellsW
What is a zygote?
A fertilised egg
What are the processes in meiosis?
- The chromosomes make identical copies of themselves
- Similar chromosomes pair up
- Pairs of chromosomes divide
- The chromosomes then divide again producing four haploid cells
What is asexual reproduction?
When cells divide by mitosis, which are genetically identical to the parent cell
What is sexual reproduction?
Meiosis where genetically identical haploid gametes fuse to form a diploid cell at fertilisation
What are the advantages of asexual reproduction?
- Can produce lots of offspring very quickly
- Only one parent is needed
What are the disadvantages of asexual reproduction?
- There is no genetic variation between offspring in the population
What are the advantages of sexual reproduction?
- Creates genetic variation in the population
What are the disadvantages of sexual reproduction?
- Takes more time and produces fewer offspring
- Two parents are needed for sexual reproduction
What are DNA strands made of?
Nucleotides
What is in a nucleotide?
A phosphate group, a sugar and a base
What are the four different bases?
A (Adenine), T (Thymine), C (Cytosine), G (Guanine)
What are the base pairs joined together by?
Weak hydrogen bonds
How do you extract DNA from fruit cells?
- Mash some fruit and put in a beaker of salt and detergent (detergent breaks down cell membrane)
- Filter the mixture
- Cool in an ice bath and add ethanol
- DNA will become a white precipitate
What is a gene?
A section of DNA that codes for a particular protein
What occurs in transcription?
- RNA polymerase binds onto the non-coding region of a gene
- It unzips the DNA and passes along a DNA strand, adding complementary base pairs to the gene
- Once made, the mRNA strand moves out of the nucleus, into the ribosomes
What occurs in translation?
- A codon codes for an amino acid
- The anticodon is complementary to a codon which is part of the tRNA molecule
- The amino acids form a polypeptide chain
What happens if there is a mutation in the non-coding region of the DNA?
- The RNA polymerase may not bind properly to the DNA strand
- It affects how much mRNA is transcribed
What did Mendel do?
- He bred a tall pea plant and a short pea plant with all the offspring being tall
- He bred two of these tall offspring plants together and found that for every small plant, there were three tall plants
What are two different alleles?
Heterozygous
What are two dominant alleles?
Homozygous dominant
What are two recessive alleles?
Homozygous recessive
What chromosomes do males have?
XY
What chromosomes do females have?
XX
What are the positives gained from the Human Genome Project?
- Prediction and prevention of disease
- Testing and treatment for inherited diseases
- New and better medicines
