Genetics Flashcards
What is genetics?
Genetics is the study of genes, genetic variation, and heredity in organisms.
Who is the Father of Genetics?
Gregor Mendel
What is Deoxyribose Nucleic Acid (DNA)?
It is the molecule that carries the genetic information for the development and functioning of an organism.
What is the DNA structure like?
It has a sugar-phosphate backbone and information contained in the sequence of bases.
The strands pair up in an antiparallel fashion.
DNA is replicated, and it is always read…
In the 5’ —-> 3’ direction
What does the double helix of DNA consist of?
Consists of two strands running in the opposite direction to each other.
What are the bonds formed between bases and what do they do?
Hydrogen bonds between the bases link the strands
What are the names of the bases?
Adenine – Thymine
Guanine – Cytosine
What are purines and two examples?
One of two chemical compounds cells use to make DNA and RNA building blocks.
-Adenine and Guanine
What are pyrimidines, and three examples?
A nitrogenous base similar to benzene (a six-membered ring)
-Thymine, Cytosine, and Uracil
What is RNA?
It stands for Ribonucleic Acid, and it is a single-stranded molecule.
What are the two main differences between RNA and DNA?
- The sugar in the backbone is Ribose, instead of deoxyribose, and the base Uracil is used instead of Thymine.
How many bases does the human genome have, and how many encode for genes?
The human genome has approximately 3 billion bases, although only a small proportion of them (1-2%) encode genes.
What are histones?
A type of protein found in chromosomes. Histones bind to DNA, help give chromosomes their shape, and help control the activity of genes.
What does the structure of DNA with histones resemble?
A ball of string
What is the structure of histone, and what is its function?
Highly basic positively charged octamer. and it makes the DNA coil further to make the chromosomal structure.
What does condensation do to the DNA?
Condensation of DNA controls gene function. Tightly coiled DNA
(condensed) is less transcriptionally active.
What chromosomes are all present in the cells?
22 pairs of chromosomes and the sex chromosomes are present in each cell.
Define DNA replication
DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule.
A DNA strand can be replicated in 2 directions, true or false?
False. A DNA strand can only be replicated in one direction.
After the strands are separated and unwound, what happens to the leading and lagging strands?
- The leading strand has bases added in the 5’ to 3’ direction by a DNA polymerase.
-On the lagging strand, short stretches of DNA are synthesized as it unwinds (called Okazaki fragments), and these are then joined by
a DNA ligase.
What are Okazaki fragments?
Short sequences of DNA nucleotides are synthesized discontinuously and later linked together by the enzyme DNA ligase to create the lagging strand during DNA replication.
What is Helicase?
DNA helicases catalyze the disruption of the hydrogen bonds that hold the two strands of double-stranded DNA together.
What do the Primase, RNA primer, and DNA polymerase do?
Primase: Synthesizes RNA primers during DNA replication.
RNA primer: Primer RNA is RNA that initiates DNA synthesis.
DNA polymerase: Adds nucleotides to the three prime (3’)-ends of a DNA strand, one nucleotide at a time.
What does ligase do?
Joins DNA fragments together, ‘the gluer’
What enzyme prevents the supercoiling of DNA?
Topoisomerase.
What are SSB proteins?
-Stands for single-stranded binding proteins.
These proteins bind to the DNA to prevent them from joining together again.
What is mitosis, and what happens to one parent cell?
The process of somatic cell division. One parent cell
becomes two almost genetically identical daughter cells.
What are the stages of mitosis?
Interphase.
Stage 1- Prophase
Stage 2- Metaphase
Stage 3- Anaphase
Stage 4- Telophase
Cytokinesis.
What happens in the Interphase, and in what part of the cycle may the cell be found?
The cells look normal at this stage.
The cell may be in G0, G1, or S phase in the cell cycle.
When is DNA replicated? (In what phase?)
S phase
What happens in prophase?
In Prophase, the chromosomes condense and form part of the mitotic spindle.
What happens in metaphase?
In Metaphase, the chromosomes line up in the center of the dividing cell. Microtubules are attached to each chromosome centromere.
Draw the structure and name the three elements formed by microtubules.
Kinetochore, Microtubule and Centromere
What happens in the anaphase?
At Anaphase, the duplicated chromosomes are separated by
contraction of the microtubules.
What happens in telophase?
During Telophase, the chromosomes reach the poles of the cell, and the two cells separate (Cytokinesis). The chromosomes
decondense and form part of the nucleus once more.
What is cytokinesis?
Cytokinesis is the physical process of cell division, which divides the cytoplasm of a parental cell into two daughter cells.
What is meiosis?
Meiosis in humans only occurs during gamete production.
What are the stages in meiosis I, and what happens in each?
Interphase: Cells are normal.
Prophase I: During Prophase in Meiosis I, homologous chromosomes pair, and there is a crossing over between the homologous chromatids.
Anaphase I: Chromosomes are pulled apart by the contraction of the microtubules.
Telophase I: Chromosomes reach the poles of the cell, and cytokinesis occurs.
Now you have two daughter cells.
What happens in meiosis II?
In Meiosis II, the second round of cell division leaves four haploid
daughter cells.
What are the stages of meiosis?
Prophase II
Metaphase II
Anaphase II
Telophase II
Daughter cells!
What is the normal chromosome structure? Draw it and label it.
Telomere, Short Arm (p Arm), Centromere, Long arm (q Arm).
What are sister chromatids?
Two chromatids held together
What are the three types of chromosomes?
- Submetacentric: Superior ones are slightly smaller.
- Metacentric: telomere close to the middle, with a shorter “p”
arm and longer “q” arm - Acrocentric: centromere at one end, with only satellite DNA on the short “p” arm.
What three things are chromosomes recognised by?
Their size, the position of the centromere and their banding pattern.
What is banding??
Chromosome banding refers to alternating light and dark regions along the length of a chromosome, produced after staining with a dye.
When are chromosomes visualized?
Metaphase
