DNA and Chromosomes Flashcards
What are the two types of cell?
- Prokaryotic Cell
* Eukaryotic Cell
How is DNA present in prokaryotic cells?
Prokaryotic Cells:
• DNA molecules are shorter
• DNA molecules form a circle
• not associated with any protein molecules
• Prokaryotic cells do not have chromosomes
How is DNA present in eukaryotic cells?
- DNA molecules are longer, form a line ( linear ), not a circle
- In association with proteins called histones to form structures called chromosomes
- Mitochondria and chloroplasts of eukaryotic cells contain DNA, which is short circular and not associated with histones
When are chromosomes visible?
- Chromosomes are only visible as distinct structures when a cell is dividing.
- Aside from this time, they are widely dispersed throughout the nucleus
How is DNA present during division?
- DNA becomes visible at the s tart of cell division
- Chromosomes appear as two threads, joined at a single point
- Each thread is a chromatid
What is a chromatid?
- A thread of a chromosome, each thread is a chromatid
* Chromosomes made up of two chromatid threads joined at a single point
What is the DNA held in chromosomes by?
Histones
How are chromosomes formed?
- DNA molecule combines with histones. helix is wound around histones to fix it in position
- DNA-histone complex is formed
- DNA-Histone complex coils fold to form loops
- Loops further coil and pack together to form the chromosome
What is formed when DNA and histones combine?
DNA-Histone Complexes
What is a gene?
Sequence of DNA bases
Either as a polypeptide or functional RNA
What forms the primary structure?
Sequence of amino acids in a polypeptide
Why is DNA turned into chromosomes?
- A lot of DNA is condensed into a single chromosomes
* Chromosome contains a single molecule of DNA
How much DNA does a chromosome contain?
Single molecule of DNA
How are genes present on the DNA molecule?
Each gene occupies a specific position ( locus ) along the DNA molecule
What causes sexually produced organisms?
Result of the fusion of a sperm and an egg
Where do the chromosomes come from in sexually produced organisms?
• Each contributes one set of chromosomes to the offspring
What are the maternal chromosomes?
Chromosomes from the mother
What are paternal chromosomes?
Chromosomes from the father
What are homologous pairs?
- Homologous pairs are made up of chromosome pairs of the same length
- A homologous pair is always two chromosomes that carry the same genes but not necessarily the same alleles of the genes
- One homologous pair is inherited from the organism’s mother.
- Another is inherited from the organism’s father
What is the diploid number
- Diploid cell is a cell that contains two sets of chromosomes
- Each chromosome pair is considered to be one set of homologous chromosomes
What type of cell are gametes?
Haploid
What is an allele?
One of a number of alternative forms of a gene
What are genes?
Sections of DNA that contain coded information in the form of specific sequences of bases
What does a change in the base sequence of a change cause?
- Produces a new allele of that gene, a mutation, and results in a different sequence of amino acids being coded for.
- Different amino acid sequence will lead to the production of a different polypeptide, and a different protein
- This protein may not function properly or may not function at all, when the protein produced is an enzyme, may have a new shape
- The new shape may not fit the substrate, leading to the enzyme not functioning
How do mutations affect the body?
- Different amino acid sequence will lead to the production of a different polypeptide, and a different protein
- This protein may not function properly or may not function at all, when the protein produced is an enzyme, may have a new shape
- The new shape may not fit the substrate, leading to the enzyme not functioning
