SB3 Separate Content Flashcards
Define sexual reproduction
The process involving the fusion of the male and female gametes, each containing genetic information from the mother or the father
What are the human gametes?
- sperm cells - male
- egg cells - female
What are the plant gametes?
- pollen - male
- egg cell - female
Describe a gamete
- haploid
- therefore contains 23 pairs
- produced through meiosis
What are the advantages of sexual reproduction?
- increases sexual variation
- species can adapt to new environmentsdue to variation, giving them a survival advantage
- disease less likely to affect population (due to variation)
What are the disadvantages of sexual reproduction?
- takes time and energy to find mates
- slow
- difficult for isolated members of a species to reproduce
Define asexual reproduction
The process in which genetically identical offspring are being produced by one parent
What are the advantages of asexual reproduction?
- no need to find a mate
- rapid reproductive cycle (if enough food available)
- If a parent is well adapted to the environment, offspring will be too
What are the disadvantages of asexual reproduction?
- limited genetic variation in population
- population vulnerable to changes in habitat and may only be suitable to one habitat
- disease more likely to affect the whole population - could cause them to be wiped out
What is a codon?
A sequence of three nucleotides (bases) in a DNA or RNA molecule that codes for an amino acid
What determines the protein produced?
The order of bases
What are the two stages in protein synthesis?
- transcription
- translation
What happens in transcription?
- RNA polymerase attaches to DNA in front of a gene in the non-coding region and the two DNA strands separate
- RNA polymerase moves along the template strand and adds complimentary bases to form messenger RNA (mRNA)
- mRNA has the base uracil rather than T, which pairs with Adenine
- mRNA leaves nucleus through pores
What are the proteins involved in transcription?
- mRNA
- RNA polymerase
What base is present in protein synthesis that is not present in DNA?
Uracil (U)
What does the base U bind with?
A
What occurs in translation?
- mRNA attaches to ribosomes in the cytoplasm
- Ribosome moves along mRNA 3 bases at a time
- at each mRNA codon, a transfer RNA with complementary bases lines up
- it carries an amino acid
- Ribosomes moves along and the amino acid joins up to form a polypeptide
- empty tRNA leaves
- Amino acids join to form a polypeptide chain which folds to form a protein. Shape is important for function
What are the proteins involved in translation?
- ribsome
- transfer RNA
- polypeptide
Where does transcription occur?
In the nucleus
Where does translation occur?
cyptoplasm
How many different types of amino acids are there?
20
Define genotype
Genes present in the DNA of an individual
Define phenotype
Genes expressed in an individual: the visible effects of a genotype
What are genetic variants?
Small changes in the order of bases that make up a strand of DNA
What are the causes of genetic mutations ?
Mistakes when DNA is copied during cell division, or environmental factors such as radiation
What is the effect of mutations in the coding region of DNA?
Will alter the structure or function of the protein produced because it will alter the sequence of bases
What is the effect of mutations in the non coding region of DNA?
Affects the binding of the RNA molecule, which affects how much of the protein is produced
How do mutations occur in the non coding region of DNA?
- RNA polymerase attaches to non-coding DNA found before genes
- Mutations here may mean that it doesn’t bind well (reducing transcription)
- Mutations here may also cause it to bind better (increasing transcription) so more mRNA made
What could be the effects of mutations in the sequence of bases in DNA?
- A base is inserted into a code
- A base is deleted from a code
- A base is substituted into a code - may not even change the amino acid, as several codons code for the same amino acid
What are stop codons?
Codons that stop translation and don’t code for an amino acid
Who was Gregor Mendel?
The monk who started modern ideas about genes
How did Gregor Mendel experiment?
Using pea plants
What are the four blood groups?
- A
- B
- O
- AB
Which blood group is the universal donor?
Blood group O
Which blood group is the universal receiver?
Blood group AB
What are the alleles for deciding blood group?
I^A, I^B, I^O
Which of the blood group alleles are dominant?
A and B
Which blood group allele is recessive?
o
What is codominance?
Blood group A and B are equally dominant, so they are both expressed, giving us blood group AB
What is a sex-linked disorder?
Disorders caused by the XX and XY alleles
Why are men more likely to have sex linked diseases?
- the Y gene is much smaller than the X
- so the Y gene has less alleles than the X, and is even missing some alleles
- therefore, if the X gene has a faulty allele, it will always be expressed if the Y gene doesn’t have the dominant counterpart
