Term 2 UNIT 4 Flashcards
DNA structure, mitosis and meiosis (32 cards)
What is Deoxyribonucleic acid (DNA)?
A double-stranded molecule that occurs bound to proteins (histones) in chromosomes.
What are histones?
Proteins found in eukaryotic cell nuclei that package and order DNA into structural units called nucleosomes.
Where is DNA located in eukaryotes?
In the nucleus.
Where is DNA located in prokaryotes?
Unbound in the cytosol (intercellular fluid).
Which organelles contain DNA?
Mitochondria and chloroplasts.
In which part of the cell is DNA found in mitochondria and chloroplasts?
Unbound in the cytosol.
True or False: Eukaryotes evolved by engulfing other prokaryotes.
True.
What is DNA made up of?
DNA is made up of molecules called nucleotides.
Nucleotides are the building blocks of DNA.
What are the components of a nucleotide?
A nucleotide contains a phosphate group, a sugar group, and a nitrogen base.
The sugar in DNA is deoxyribose.
What are the four types of nitrogen bases in DNA?
- Adenine (A)
- Thymine (T)
- Guanine (G)
- Cytosine (C)
These bases are critical for the structure of DNA.
Which nitrogen bases pair together in DNA?
Adenine pairs with thymine, and guanine pairs with cytosine.
This pairing is known as complementary base pairing.
What type of bonds keep the strands of a DNA helix together?
Hydrogen bonds between complementary nucleotides.
These bonds are essential for the stability of the DNA structure.
What are somatic cells?
Somatic cells are ‘body’ cells that contain the normal number of chromosomes, called the ‘diploid’ number.
In humans, somatic cells have 46 chromosomes.
What are gametes?
Gametes are the ‘sex’ cells that contain only ½ the normal number of chromosomes, called the ‘haploid’ number.
For humans, gametes have 23 chromosomes.
What is the diploid number of chromosomes in humans?
2n=46.
This represents the total number of chromosomes in somatic cells.
What is the haploid number of chromosomes in humans?
n=23.
This represents the number of chromosomes in gametes.
What is a homologous pair of chromosomes?
A pair of chromosomes (maternal and paternal) that are similar in shape and size
Each locus (position of a gene) is in the same position on homologues. A homologous pair consists of 4 chromatids, called a ‘tetrad’.
What is MONOSOMY?
The condition where an organism has only one chromosome in a particular set
For example, monosomy 23 means having one chromosome in the 23rd set.
What is TRISOMY?
The condition where an organism has three chromosomes in a particular set
For example, trisomy 18 means having three chromosomes in the 18th set, and trisomy 21 means three chromosomes in the 21st set.
What is DNA replication?
The process by which DNA makes a copy of itself during cell division
What is the role of helicase in DNA replication?
To ‘unzip’ the double helix structure of the DNA, creating a Y-shaped replication fork
What characterizes the leading strand in DNA replication?
It is oriented in the 3’ to 5’ direction towards the replication fork
What characterizes the lagging strand in DNA replication?
It is oriented in the 5’ to 3’ direction away from the replication fork
What is a primer in DNA replication?
A short piece of RNA produced by primase that binds to the end of the leading strand
