STRUCTURE AND FUNCTION OF GENES, CHROMOSOMES AND GENOMES Flashcards
1
Q
What is genome?
A
- Genome is a complete set of genetic information in an organism.
- It provides all information for an organism to function.
- There are 2 types of genome which are nuclear genome and mitochondrial genome.
- Nuclear genome can be found in nucleus and it has 23 pairs of chromosomes.
- Nuclear genome also come from paternal and maternal.
- It is in a linear or double stranded shape.
- However, mitochondrial genome can be found in the mitochondria and it has several copies of mtDNA.
- It is obtained from the maternal.
- Mitochondrial genome is in a circular shape
2
Q
List 5 factors that contributes to the size of genome and complexity.
A
- Pseudogene
- Gene families
- Number of genes in a genome
- Repetitive DNA sequence
- Introns and exons
3
Q
Describe how DNA is packaged into a chromosome.
A
- There are 3 levels of DNA packaging.
- Firstly, the DNA wraps around histone forming nucleosome.
- Then, multiple histones wrap around the DNA forming chromatin fibre.
- In the chromatin fibre, there are nucleosomes which are in a compact form.
- Then, in a higher level, the chromatin fibre is condensed and formed a chromosome.
4
Q
Describe how the eukaryotic DNA is packaged into a chromosome.
A
- In eukaryotic, the histones proteins have 5 families which are H1,H2A,H2B,H3,H4.
- H3 and H4 are going to form a tetramer which contains 2 molecules of H3 and H4 each.
- However, H2A and H2B are going to form a dimers.
- The histones form are octamer.
- The special role of H1 in this eukaryotic DNA packaging is to bind to the DNA entering and exiting the nucleosome.
- Other than that, it also helps in maintaining the chromatin structure.
5
Q
State 4 functions of chromatin
A
- To package DNA into smaller volume to fit into the cell
- To strengthen the DNA for mitosis
- To prevent DNA damage
- To control gene expression and DNA replication
6
Q
Describe the chromosome structure.
A
- In human body, there are 23 pairs of chromosome where 22 of them are autosomes and the remaining is the sex chromosomes.
- In chromosomes, there are centromere, telomere, and kinetochore.
- Centromere is located at the middle of the chromosomes.
- Centromere connects the chromatids and dividing the chromosomes to 2 arms which is called p for the shorter arm and q for the longer arm.
- In the centromere, there are many repetitive DNA that is responsible for movement of chromosomes during the mitosis process.
- The centromere is where the mitotic spindles attach to pull the homologous chromosomes apart during mitosis.
- Other than that are telomere. Telomere is located at the end of the chromosomes which act as a protective caps.
- Telomere has the base sequence TTAGGG
- In fact, telomere has an enzyme called telomerase that going to function when the telomere is worn out such as during old time.
- The telomerase will restore back the length of telomere when it is worn out.
- The functions of telomere are to prevent end-to-end fusion of chromosomes, protecting the end of the chromosomes from degradation and ensuring that the DNA replication is complete.
- Lastly, kinetochore is located at the side of the telomere where the spindle microtubule is attached during mitosis and meiosis.
- The kinetochore contains 2 region which are inner and outer region.
- Inner region is where it tightly associated with the centromere DNA.
- Outer region is where it interacts with microtubules.
7
Q
State the function of centromere.
A
Attach the mitotic spindles to pull the homologous chromosomes apart during mitosis.
8
Q
State the function of telomere.
A
- To prevent end-to-end fusion of chromosomes.
- To ensure that the DNA replication is complete
- To protect the end of the chromosomes from degradation.
9
Q
State the function of kinetochore.
A
- To allow the spindle microtubule to attach during mitosis and meiosis
10
Q
Describe the chromosome classification.
A
- Chromosome can be classified based on the centromere location such as telocentric, acrocentric, submetacentric, and metacentric.
- As for example, the chromosome 1 which is the largest chromosome is classified as metacentric.
- Metacentric is where the centromere is located at the middle of the chromosomes.
- While, chromosome Y which is the smallest chromosome is classified as acrocentric.
- Acrocentric is where the centromere is located close to the end of the chromosome.
- Chromosome Y is short and it involves in male sex determination and development.
- However, chromosome X which is more larger than chromosome Y is active in female.
- Chromosome X is classified as submetacentric where the centromere is located between the middle and end of the chromosomes.
11
Q
What is gene?
A
Genes are the segments of DNA located on chromosomes that contain the instructions for protein production.
12
Q
Describe the regions of gene involved in gene expression.
A
- Firstly, the regions of gene involved in gene expression is exons.
- Exons is the region that is used during transcription and translation.
- DNA is used as a template to create mRNA is called transcription.
- After transcription is done, to produce a protein, the immature mRNA have to be translated via tRNA.
- Next region is the introns which are non coded region.
- In this region, the function is unknown within a gene that specifically interrupts the coding sequences of that gene.
- The introns are transcribed but removed from the pre-mRNA by a splicing mechanism.
- Promoter also one of the region involve in gene expression.
- Promoter is the regulatory region of DNA.
- The core promoter region consist of TATA box and CAAT box.
- TATA box is where the polymerase II bind and various transcription factor.
- CAAT box is where the RNA transcription factor bind.
- Enhancer is the region where it enhance the transcription level of a gene.
- Enhancer is the positive transcriptional control elements
- However, silencer is the region where it prevent the transcription process from happening. Thus it suppress the RNA synthesis.
- Lastly, the terminator region is where the transcription process stop.
- Terminator is the end mark for transcription of DNA.
13
Q
List the disease caused by DNA structure abnormalities
A
- Duchenne muscular dystrophy (DMD)
- Becker muscular dystrophy
14
Q
What caused the Duchenne Muscular Dystrophy (DMD)?
A
- It is due to the failing in producing functional dystrophin gene located at chromosome X
- Due to fail in producing any functional dystrophin, the muscles cells are easily damaged and eventually die.
- This also can lead to side effects to the heart and lungs.
15
Q
What causes the Becker Muscle Dystrophy?
A
- BMD occur when the dystrophin gene is manufactured but not fully function.
