Chromosones, Genes And DNA Flashcards
(28 cards)
Define heterochromatin
Genes are not expressed in this form and DMA is packaged onto solenoid fibres.
Define Euchromatin
Genes are expressed in this form and DNA is on beads on a string form.
What is a gene?
A length of DNA that carries a code for a protein.
How are nucleotides joined?
Phosphodiester bonds in a 5’ to 3’ direction.
Name the pyrmadines
Cytosine, Uracil, thymine
Name the purines?
Guaine, adenine.
How large is a turn of the DNA double helix?
3.4 nm
How many hydrogen bonds between A and U?
2
How many hydrogen bonds between g and c?
3
What is the sequence of gene expression?
DNA ➡️ RNA ➡️ Protein
Explain how DNA replicates in the human body?
Moving replication fork created by DNA helicase, which unwinds the double helix. DNA polymerase extends the 3’ ends only, leading to a continuous leading strand and a discontinuous lagging strand consisting of Ozaki fragments. Termination occurs when two replication forks meet, and the Ozaki fragments are joined by DNA ligase .
What is the direction of DNA replication, and the enzyme that performs DNA replication?
5’ to 3’ direction, and the enzyme that performs it is DNA polymerase .
What are the stages of mitosis?
Prophase, prometaphase, metaphase, anaphase, telophase.
What are the stages of meiosis?
Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II and Telophase II.
What are the consequences of meiosis?
4 daughter cells, as well as maintaining a constant chromosome number from generation to generation, and creation of genetic diversity through independent assortment and crossing over.
What are the cells at each cell of spermatogenesis?
Spermatogium, primary spermatocyte, spermatids, and mature sperm.
What are the products of oogenesis?
A mature ovum and 3 polar bodies
Define heterozygous
Two alleles of a gene are different
Define homozygous
When the two alleles of a gene are the same
Define Hemizygous
Only one gene on the X chromosome
What are some key features of an autosomal recessive pattern of inheritance?
Heterozygotes unaffected, males and females equally affected, 2 heterozygotes can only have affected offspring whereas two carriers have a 25% chance of affected offspring. Can appear to spring up out of nowhere.
What are the key features of a autosomal dominant pattern of inheritance?
Males and females equally affected, rarely found in a homozygous state, cannot skip generation, every affected person will have affected parents.
What are the key features of X linked recessive inheritance?
Hemizygous males and homozygous females, every heterozygous female has a 50% chance of affected children, more common in males, affected males cannot pass the gene to sons.
What is co-dominance?
When neither gene is dominant over another
