Inheritance Flashcards
What is the genome?
All of the genes present in an organism.
What is a gamete?
Gametes are sex cells (sperm or eggs).
What is a chromosome?
Tightly packaged DNA around histone proteins.
How many chromosomes do human body cells have?
46 chromosomes (23 pairs)
How many chromosomes do human gametes have?
23 chromosomes
Where are chromosomes located?
In the nucleus of the cell
What is a gene?
A section of DNA that codes for a protein.
Describe the structure of DNA
- It is a polymer made of many nucleotide monomers
- It is made of 2 strands in the shape of a double helix
Name the 4 bases in DNA
- Adenine (A)
- Thymine (T)
- Cytosine (C)
- Guanine (G)
State 2 differences between DNA and RNA?
- DNA is double stranded whereas RNA is single stranded
- RNA contains Uracil (U) whereas DNA contains Thymine (T)
How do the bases in DNA pair up?
Adenine pairs with Thymine (A with T)
Cytosine pairs with Guanine (C with G)
Describe transcription
1) DNA unzipped
2) Complementary mRNA nucleotides bind and are joined together
3) mRNA detaches and leaves the nucleus
What is a codon?
A group of 3 bases on the mRNA molecule that code for a single amino acid.
What is an anticodon?
3 bases on a tRNA molecule that match the codon on the mRNA molecule
Describe translation
1) mRNA travels to a ribosome
2) tRNA molecules with an anticodon that matches the codon on the mRNA molecule carry amino acids to the ribosome
3) The amino acids are joined together
How does the sequence of bases affect the protein made in protein synthesis?
DNA is a triplet code where 3 bases code for one amino acid and the order of amino acids determine the protein produced.
What is an allele?
Different versions of the same gene
What is a dominant allele?
A version of a gene where only one copy is needed for it to be expressed.
A version of a gene where only one copy is needed for it to be expressed.
A version of a gene where two copies are needed for it to be expressed
What is meant when an organism is homozygous?
When an organism has two copies of the same allele (two recessive or two dominant).
What is meant when an organism is heterozygous?
When an organism has two different versions of the same gene (one dominant and one recessive).
What is the genotype?
The genes present for a trait
What is the phenotype?
The visible characteristic
What is codominance?
When two alleles affect the phenotype
What is monohybrid inheritance?
The inheritance of one allele
Draw a Punnett square for a cross between a homozygous recessive blue eyed female (bb) with a heterozygous brown eyed male (Bb)
Draw a Punnett square for a cross between a homozygous dominant red flower (RR) with a homozygous recessive white flower (rr)
Draw a Punnett square for a cross between two heterozygous cystic fibrosis carriers (Ff)
Draw a Punnett square to show how sex is determined
What do family pedigrees show?
Give 3 processes that require mitosis
- Growth
- Repair
- Asexual reproduction
How many cells does mitosis produce?
One parent cell produces two daughter cells.
How many cells does meiosis produce?
One parent cell produces 4 daughter cells.
Give 2 differences between mitosis and meiosis
- Mitosis produces 2 genetically identical cells whereas meiosis produces 4 genetically different cells
- Mitosis produces diploid cells whereas meiosis produces haploid cells
What is random fertilisation?
- The random chance of a specific sperm combining with a specific egg
- This increases variation as any female can mate with any male and any one of the millions of sperm could fertilise the egg
What are the two types of variation?
Genetic variation and environmental variation
State 2 traits in humans caused only by genetic variation
- Eye colour
- Blood type
State 2 traits in humans caused by a mix of environmental and genetic variation
- Height
- Weight
What is a mutation?
A random change in the genetic material of an organism.
How do mutations alter the phenotype?
- Mutations alter the genetic material (DNA)
- This can cause it to code for a different sequence of amino acids
- A different sequence of amino acids means that the protein will be different
Give 3 environmental factors that can increase the chance of mutations
- Exposure to UV radiation
- Exposure to X-rays
- Certain chemicals, particularly those found in cigarette smoke
Describe the process of natural selection
- Populations are naturally varied due to random genetic mutations
- Some of these mutations provide a selective advantage
- These organisms survive and reproduce, passing on the successful genes
Define evolution
Evolution is a change in the genetic makeup of a population over time due to natural selection.
Describe how antibiotic resistance arises
- A random genetic mutation causes a bacterium to become resistant to the antibiotic
- When the antibiotic is used, all the bacteria that do not have the mutation are killed
- The population containing just the resistant bacteria then begins to grow
What are the risks of antibiotic resistance?
Bacteria that cause infections that are resistant to antibiotics are hard to treat and can pose a serious threat to our health.
