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Lecture 2

ANTA01H3 Lecture Notes - Lecture 2: Dna Replication, Spindle Apparatus, Centromere

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ANTA01 -Lecture 2: Biology, Evolution, Anthropology
Genetics: the study of how genes work and how traits are passed from parent to
Genetic mechanisms are the foundation for evolutionary change.
DNA is the very basis of life (“building blocks of all life-forms”) because it directs all
cellular activities, and is responsible for an organism’s inheritance
Protein synthesis
Cell division (DNA replication)
Cell biology- we are all composed of cells. Cellular function, division. Our bodies have
functions going on controlled by DNA. DNA is the building block of live. Responsible for
human synthesis.
Chromosomes on their own exist as a single structure but once replicated it is double
stranded. Chromosome is made up of smaller genes. They are connected together by a
Chromosomes genes DNA
Nucleotide base pairs gene chromosome fragment
Scanning electron micrograph of human chromosomes.
Note that these chromosomes are composed of two strands, or two DNA molecule
(during cell division only).
This is when we are visually see the chromosome under the microscope, not single
CHROMOSOME: a very long DNA molecule and associated proteins, that carry portions
of the hereditary information of an organism.
Structure of a chromosome:
A chromosome is formed from a single DNA molecule that contains many genes. A
chromosomal DNA molecule contains three specific nucleotide sequences which are
required for replication: a DNA replication origin; a centromere to attach the DNA to the
mitotic spindle.; a telomere located at each end of the linear chromosome.
Karyotype of a male:
The human haploid genome contains 3,000,000,000 DNA nucleotide pairs, divided
among twenty two (22) pairs of autosomes and one pair of sex chromosomes.
23 pairs in a regular body cell except reproductive cells. 1 pair in sperm and gamete.
A chromosome is composed of a DNA molecule and associated proteins
During normal cell functions, chromosomes exist as single-stranded structures (46 in
During cell division, chromosomes consist of two strands of DNA joined at the
Since the DNA molecules have replicated, one strand of a chromosome is an exact copy
of the other.
46 single chromosomes except when replicated
Gene is section of chromosome.
Responsible for Protein synthesis
A gene can be defined as a region of DNA that controls a hereditary characteristic
(alleles are variant forms of a gene). It usually corresponds to a sequence used in the
production of a specific protein or RNA.
Each dark band is gene.
DNA is composed of two chains of nucleotides, comprising a double strand or double
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A nucleotide consists of a sugar, a phosphate, and one of four nitrogenous bases.
Nucleotides (basic units of the DNA molecule, composed of a sugar, a phosphate, and
one of four DNA bases) form long chains.
The two chains are held together by bonds formed on their bases with their complement
on the other chain.
Adenine (A) is the complement of Thymine(T)
Guanine(G) is the complement of Cytosine(C)
Nitrogen bases are important for reproduction of cells.
Uncoiled chromosome are made up of the four bases. Make up the ladder of DNA
Cause of variation is in the variation in our genes.
DNA can replicate so cells are forming and the body can produce proteins.
Essential function of genes is protein synthesis. Key function of DNA.
One of the most important activities of DNA is to direct the assembly of proteins (protein
synthesis) within cells (assembling chains of amino acids into functional protein
Proteins are made up of chains of smaller molecules called amino acids. In all, there are
20 amino acids, 8 of which must be obtained from foods. These are known as essential
amino acids. The remaining 12 are produced in cells and are known as nonessential
amino acids. These 20 amino acids are combined in different amounts and sequences to
produce at least 90,000 different proteins. What makes proteins different from one
another is the number and sequence of their amino acids.
In part, DNA is a recipe for making a protein, because it’s the sequence of DNA bases
that ultimately determines the order of amino acids in a protein.
1st process of protein synthesis is transcription. 2 nd processes translation.
Transcription of DNA to RNA to protein- DNA turns to mRNA. DNA cannot physically
leave the nucleus. mRNA goes into cytoplasm and meets up with ribosome. Ribosome is
where protein synthesis is happening. Translation occurs. Nitrogen base codes are
translated. Transfer RNA
Mitosis- only in body cells. 46 singular chromosomes to 46 double stranded
Meiosis sex cells, 2 separate states of division. 2 stages in gametes. Have to be paired
up with an another one in the future. Cell with half the number of chromosome. 46 single
then 23. 2 daughters 23 chromosomes from 23 mother chromosomes.
Results in variation and diversity than mutation. Mutation happen at a relative low rate in
regard to sex cells.
Heredity and evolution-
1) overproduction- Every species tends to produce more individuals than can survive to
2) Variation- the individuals of a population have many characteristics that differ
3) Selection- some individuals survive longer and reproduce more.
Selective breeding of pea plants (practice whereby animal or plants breeders choose
which individual animals or plants will be allowed to mate based on the traits they hope
to produce in the offspring)
Animals/plants without desirable traits are not allowed to breed.
Hybrids: offspring of parents that differ from each other with regard to certain traits or
certain aspects of genetic makeup; heterozygotes.
Did what a lot of dog breeders do today.
Interested in hybrid offspring.
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