0210 Mitosis, meiosis and the cell cycle Flashcards
What is a chromosome
Chromosomes are linear structures made up of tightly packed, coiled DNA and histones. They are found in the nucleus and carry genetic information
What is the name given to tightly packed chromatins (AT rich) and loosely packed chromatins (GG rich, gene rich)
Heterochromatin = tightly packed chromatin Euchromatin = loosely packed chromatin
How many chromosomes are contained in the human nucleus
46 chromosomes. 23 pairs. 22 pairs of autosomes and 1 pair of sex chromosomes
What are the 4 main enzymes that play roles in DNA replication
DNA polymerase, helicase, primase and DNA ligase
What is the role of DNA polymerase
DNA polymerase produces complementary strands of DNA in a 5’ - 3’ direction (extension). It also monitors the addition of nucleotides to avoid errors (excision/proofreading)
What is the role of Helicase
Their function is to move down DNA separating the double helix into two strands of DNA
What is the role of primase
Primase synthesis of primer which initiates DNA polymerase coding
What is the role of ligase
Ligase joins fragments of nucleic acid in the lagging strand of DNA replication
What is the difference between the leading and lagging strand of DNA during replication (hint: think function of DNA polymerase)
DNA polymerase moves down the leading strand 5’-3’ (in one movement). DNA polymerase moves downt the lagging strand 3’-5’ (multitude of movements)
True or False - DNA polymerase in the leading strand (5’-3’) moves away from the fork (point where the helix is being separated)
False (leading strand moves towards the fork)
Which of the parents (maternal or paternal) have the biggest influence on the risk factors of trisomy 21 (down syndrome)
Maternal. As the age of the mother at delivery increases so does the incidence of trisomy 21. A carrier patients also have a much higher rate of incidence
Briefly describe mitosis
Mitosis is the replication division of normal (somatic) cells in their cell cycle. All cells replicate in this manner except for gametes. The product is a diploid cell (2n)
Briefly describe meiosis
Meiosis is the reduction division of gametes (sex cells). It produces haploid cells (n)
When in the cell cycle does DNA replication occur
DNA replication occurs during the interphase (S phase) of the cell cycle
`What are the 5 types of chromosomal rearrangements? Which of these a single chromosome changes and which of these are paired
Single - Deletion, duplication, inversion
Paired - insertion, translocation
What is the definition of balanced and unbalanced structural chromosomal changes
Balanced changes = no net gain or loss of chromosomal material and no therefore no phenotype
Unbalanced changes = net gain or loss in chromosomal material and therefore a high chance of phenotype
What is the definition of a gene? What is gene expression?
A gene is a segment of DNA which codes for a functional RNA or protein. Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product
List some factors that can influence gene expression
DNA mutation, environment, aging, food, toxins, injury, infection and drugs
True or False - 2 people with the same genotype for a feature will always show the same phenotype
False. Even though they have the same genotype the genes need to be expressed. Gene expression can be influenced by factors DNA mutation, environment, aging, food, toxins, injury, infection and drugs
What is the role of leptin? What is a consequence of decrease levels of leptin in mice
Leptin is a hormones that regulates total body fat by regulating hunger sensation and stimulating metabolism. Decreasing leptin levels in mice causes obesity (leptin is an appetite suppressor)
