Welcome To Learn Biology Online!
I have put together All the info you need to know about biology.
Welcome To Learn Biology Online!
Welcome To Learn Biology Online!
I have put together All the info you need to know about biology.
Genetics
Genetics is the science of inheritance from one generation down to the next.
Genes are passed from the adult cells to the forming zygote. A gene is a length of DNA that determines a particular characteristic of an organism. A gene can be pinpointed to a specific location called the loci on the chromosome. Not all genes can be pinpointed to a specific loci, for example your height is determined by several genes.
The human genome is split into 23 chromosomes. But each cell has copies of each cell, one from the mother and one from the father giving the offspring 46 chromosomes. Alleles are different versions of a gene. Because the 23 chromosomes comes from each parent, the offspring would have two different copies of a chromosome and more specific, two different genes (alleles). It is because the offspring has two different alleles, it is able to have genetic variation.
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| As you can see there are a total of 46 chromosomes, 23 from the mother and 23 from the father. |
GENOTYPE
Genotype is the genetic makeup of the organism, the DNA sequence.
Heterozygote is when an organism has two DIFFEERENT alleles at a loci.
Homozgote is when the organism have two of the same alleles at a loci.
PHENOTYPE
-Phenotype is the physical expression hat is given from a gene.
-When the individual is in a heterozygote stage and one allele is expressed it is call the dominant allele. The allele that is not expressed it is called a recessive allele.
-An upper case letter (A) stand for dominant and lower case letter (a) stands for recessive.
-Sometimes there is a mix of both alleles, it is called Incomplete Dominance. An example of this would be a flower that has the red allele R and white allele W. You will get RW which will give the flower a mixture of both red and white, pink. In Incomplete Dominance a blend of the alleles is expressed.
-Codominance is when both alleles are expressed. and example of this would be with blood. Type A, B and O stand for the antigen present on the surface of the red blood cell. The three alleles are IA
IB and i. IA and IB are codominant so they will cause the red blood cell the express both antigen NOT a mixture of them.
The rhesus factor is another antigen used for blood typing. A cell is Rh positive having the alleles of RhD RhD or RhD Rhd and it can be negative by having Rhd Rhd.
Microbiology
VIRUSES.
An obligate intracellular parasite.
This means that they are ONLY able to reproduce WITHIN a cell.
Outside the cell they are without activity and cannot perform any of the life functions on there own. They are not cells or even called living organisms.
A virus contains a nucleic acid genome inside a protein shell. Once the virus enters the cell it uses its genome to replicate its genome and protein, although the nature of each may vary between different viruses.
A viral genome may consist of DNA or RNA. It can be single or double stranded or linear or circular. Viruses utilize every type of nucleic acid as its genome but a given virus can only have one type of nucleic acid as its genome.
SIZE is a limiting factor for viruses. They are smaller than the host that they infect. The exterior protein of a virus is typically a rigid structure that wont expand to fit any larger genome. Even though there size is limited you would wonder how they are able to pack all the material needed to carry out reproduction, viruses rely on host-encoded proteins for translation, transcription and replication.
Viruses have the ABILITY to encode more than one protein in a certain length of genome. The can this by having more than one reading frame within a piece of DNA.
Most animal viruses have an ENVELOPE. This EXTERIOR membrane is derived from the INTERIOR membrane of the host cell. This envelope is acquired through budding of the host cell. Viruses that do not have an envelope are called naked viruses. Phages and plant cells are of this type of virus.
BACTERIOPHAGE LIFE CYCLE (VIRUSES THAT INFECT BACTERIA)
1. ATTACHMENT -binding to the exterior bacteria
2. PENETRATION -genome released into the cell while the protein coat stay outside the cell
3. The virus can now enter LYTIC OR LYSOGENIC CYCLE
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