30 Questions
What are the three parts that make up a nucleotide?
Phosphate group, Deoxyribose sugar, Nitrogenous Base
Name the four nitrogenous bases that form the 'rungs' of the DNA ladder.
Adenine, Thymine, Cytosine, Guanine
What is the process called when nuclear membranes form around the two sets of separated chromosomes?
Cytokinesis
What are the two types of nitrogenous bases and their examples?
Purines (Adenine and Guanine) and Pyrimidines (Thymine and Cytosine)
How are the nitrogenous bases held together in the DNA structure?
By Hydrogen bonds
What term describes the outcome when one cell becomes two identical cells after cell division?
Identical
Match the structure to its function: centromere
Region on chromosomes where spindle fibres can attach
What type of bond holds the sugar-phosphate backbone of DNA together?
Covalent bonds
What is a karyotype and how do geneticists use it?
A karyotype is an illustration of the chromosomes in a cell. Geneticists use it to identify chromosome abnormalities.
Match the structure to its function: spindle fibre
Thread-like tubules that attach to centromeres and centrosomes to move chromosomes
Match the structure to its function: cell plate
Helps to form the cell wall from the growing formation of vesicles
What are the three major checkpoints found in the cell cycle?
G1, G2, and M phases
What is the difference between metaphase I and metaphase II?
Metaphase I - homologous pairs (tetrads) line up at equator. Metaphase II - double stranded chromosomes line up individually at equator.
What is the difference between anaphase I and anaphase II?
Anaphase I - double stranded chromosomes (homologous chr.) move to opposite ends of the cell. Anaphase II - sister chromatids move to opposite ends of the cell.
How are haploid cells different from diploid cells in humans?
Haploid cells have HALF the # of chromosomes from the parent cell.
What are homologous chromosomes?
Matching chromosomes with similar characteristics.
Do homologous chromosomes have the same number of genes?
YES
What are two key features of meiosis that contribute to genetic variations?
CROSSING OVER of homologous chromosomes at chiasmata (tetrad) - Prophase I. Homologous chromosomes (tetrad) lining up randomly along equator (independent assortment) - Metaphase I.
What is the probability of having an aa genotype in the F1 generation if a couple have genotypes Aa and aa for a trait?
50%
Explain why the parents in the Drosophilia cross must be heterozygous to get a 3:1 phenotypic ratio.
The parents must be heterozygous to ensure a 3:1 phenotypic ratio in the offspring. This is because heterozygous parents produce a mix of dominant and recessive alleles in their gametes, leading to a 3:1 phenotypic ratio in the offspring.
If two heterozygous red-fruited tomato plants were crossed, what is the chance of getting a yellow fruit?
25%
In the houseplant Coleus, which type of leaf curve (deep or shallow) is dominant?
Deep curves (D) are dominant over shallow curves (d).
What type of wings would the offspring have if two Drosophila with genotypes Nn and Nn were crossed?
Normal wings
If a plant with homozygous deep-curved leaves is crossed with a plant with shallow curved leaves, could any of the offspring have shallow curved leaves?
No, all the offspring will have deep-curved leaves.
What is the difference between dominance and incomplete dominance in terms of allele expression?
In dominance, one allele is fully expressed regardless of homozygosity, while in incomplete dominance, both alleles are partially expressed, creating a third phenotype.
Explain the concept of codominance and how it differs from incomplete dominance.
In codominance, both alleles are fully expressed, creating a third phenotype distinct from the homozygous phenotypes, unlike in incomplete dominance where a blend is formed.
What are the possible genotypes for type A blood and how do they differ?
The possible genotypes for type A blood are IAIA and IAi. They differ in terms of homozygosity for the A allele.
Explain why blood type O has only one genotype and what that genotype is.
Blood type O has the genotype ii because it lacks the A and B antigens. It can only be inherited through two recessive alleles.
Based on the information provided, what must be the genotype of the mother if the child has blood type O?
If the child has blood type O, the mother must have the genotype ii, as blood type O is inherited through two recessive alleles.
If the father's genotype is IBi, what are the possible blood types of the child?
The child can have blood type A or B, as the father's genotype IBi can pass on either the A or B allele.
Study Notes
DNA Structure
- The model of DNA was developed by James Watson and Francis Crick.
- DNA is shaped like a double helix.
- A nucleotide is the building block of DNA, composed of three parts:
- Phosphate group
- Deoxyribose sugar (5-C sugar, also known as pentose sugar)
- Nitrogenous base (ATCG)
- The sugar in DNA is called deoxyribose sugar.
- There are two types of nitrogenous bases:
- Purines (2 N rings): Adenine and Guanine
- Pyrimidines (1 N rings): Thymine and Cytosine
- The four nitrogenous bases that form the "rungs" of the ladder are:
- Adenine
- Thymine
- Cytosine
- Guanine
- Adenine always pairs with Thymine, and Guanine always pairs with Cytosine.
- The nitrogenous bases are held together by hydrogen bonds, and the sugar-phosphate backbone is held together by covalent bonds.
Human Karyotype
- A karyotype is an illustration or photograph of the chromosomes in the nucleus of a somatic cell in an organism.
- Chromosomes are sorted into their homologous pairs by size, centromere location, and banding patterns.
- Geneticists use karyotypes to identify chromosome abnormalities.
- During cytokinesis, the cell divides into two identical cells.
Regulation of the Cell Cycle
- The timing and rate of cell division in different parts of a plant or animal are crucial to normal growth, development, and maintenance.
- The frequency of cell division varies with the type of cell.
- The cell cycle is regulated at certain checkpoints by both internal and external controls.
- There are three major checkpoints in the G1, G2, and M phases.
Mitosis
- During prophase, the centromere helps to form the cell wall, and the spindle fibers help to organize the tubules.
- The centromere is the region on chromosomes where spindle fibers attach.
- The cell plate is formed during telophase.
Meiosis
- Metaphase I: Homologous pairs (tetrads) line up at the equator.
- Metaphase II: Double-stranded chromosomes line up individually at the equator.
- Anaphase I: Double-stranded chromosomes (homologous chromosomes) move to opposite ends of the cell.
- Anaphase II: Sister chromatids move to opposite ends of the cell.
- Haploid cells have half the number of chromosomes from the parent cell.
- Homologous chromosomes have the same number of genes.
- Crossing over of homologous chromosomes at chiasmata (tetrad) and independent assortment of homologous chromosomes contribute to genetic variations.
Genetics
- In dominance, one allele is fully expressed in the phenotype of an individual.
- In incomplete dominance, two different alleles are partially expressed in the phenotype of a heterozygous individual.
- In codominance, both alleles are fully expressed in a heterozygous individual, creating a third phenotype that is unlike either homozygous phenotype.
- The probability of a particular genotype or phenotype can be determined using Punnett squares.
- Genotypes can be determined by analyzing the phenotype of offspring and their parents.
Test your knowledge on DNA structure and nucleotides with this quiz. Learn about the building blocks of DNA, the shape of DNA, and the people responsible for the model of DNA. Identify the components of a nucleotide and understand the different types of nitrogenous bases.
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