Genetics 2.2 Flashcards
What is DNA made out of?
DNA is a polynucleotide made up of lots of nucleotides joined together. Each nucleotide is made from a pentose sugar (5 carbon atoms), a phosphate group and a nitrogenous base.
The sugar in DNA nucleotides is deoxyribose sugar
What are the 4 possible bases?
A, T, C, G
What do two polynucleotide strands join together to form?
A double helix
What is the structure DNA?
A phosphate group attached to a sugar (deoxyribose sugar) attached to a base. The base is the thing that changes.
What bond do two polynucleotides join together to make?
Hydrogen bonds
Describe how DNAs structure makes it good at its job.
DNA molecules are very long and are coiled up very tightly, so a lot of genetic information can fit into a small space in the cell nucleus.
DNA molecules have a paired structure, which makes it much easier to copy itself.
Double helix makes it very stable.
How is DNA stored in eukaryotic cells?
Eukaryotic cells contain linear DNA molecules that exist as chromosomes (thread-like structures) each made up of one long molecule of DNA. The DNA has to wound around proteins (histones). The DNA (and protein) is then coiled up very tightly to make a compact chromosome.
How do DNA molecules in prokaryotic cells differ from those in eukaryotic cells?
DNA molecules in prokaryotic cells are also carried as chromosomes, but the DNA molecules are shorter and circular.
The DNA isn’t wound around proteins, it condenses to fit in the cell by supercoiling.
What do genes code for?
Proteins (polypeptides)
How many bases code for an amino acid?
3
What are exons and introns?
Exons: sections of DNA that code for amino acids
Introns: sections of DNA that don’t code for amino acids
When are introns removed?
During protein synthesis
Give an example of a flow chart to show how DNA determines our nature and development.
DNA sequence Proteins and Enzymes enable Metabolic
Determines Enzymes Metabolic Pathways
Amino acid —> Formed —–> pathways ——-> determine
Sequence Nature and
development
What are mutations, and what can they produce?
Mutations are changes in the base sequence of an organisms DNA. So, mutations can produce new alleles.
What do gametes join together to form in fertilisation?
A zygote
What is the diploid number for normal body cells?
2n
Name a haploid cell
Sperm, egg
What is the haploid number of chromosomes?
n
How many gametes are formed in meiosis?
4
Outline the steps of meiosis.
The DNA unravels and replicates itself, so there are two copies of each chromosome.
The DNA condenses to for double armed chromosomes made two sister chromatids.
Meiosis 1 the chromosomes arrange into homologous pairs, the pairs then separate, halving the chromosome number.
Meiosis 2, the pairs of sister chromatids that make up each chromosome are separated, four haploid cells that are genetically different are formed.
How does meiosis produce cells that are genetically different.
- Crossing over of chromatids
2. Independent segregation
What is a genetic bottleneck?
An event that causes a big reduction in population, which reduces the number of different alleles in a population.
Name a type of bottle neck.
The founder effect. It describes what happens when a few organisms from a population start a new colony.only a small number of organisms have contributed to the gene pool.
What is selective breeding?
When humans selectively reproduce to organisms together in order to produce higher yielding breeds. Once an organism with the desired characteristics has been produced, only that type of organism will continually be bred. This reduces the number of alleles in the gene pool.
What are the pros and cons of selective breeding?
Pros: high yielding plants and animals
Can be used to produce organisms with an increased resistance to disease. (So farmers use fewer drugs/pesticides)
Increased tolerance of bad conditions
Cons:can cause health problems, lower life expectancy
Reduces genetic diversity.
