Discussion Forum--Anthropology 1(need high quality assignment!!)

T H E B I O L O G I C A L B A S I S O F L I F E

CHAPTER 3 ANTH 1 FALL 2016

THE CELL

• Cells are the basic units of life in all living organisms.

• From single celled bacteria to us!

• An adult human has of perhaps as many as 1 trillion cells, all working together and serving their unique purpose

CELLS

CELLS

• Life on earth can be traced back 3.7 billion years

to single celled organisms, such as bacteria and

blue-green algae.

• Eukaryotic cells, cells with a nucleus, appeared 1.2

billion years ago.

• A three-dimensional structure composed of carbohydrates,

lipids (fats), nucleic acids, and proteins

CELLS

• Somatic cells – cellular components of body

tissues, such as muscle, bone, skin, nerve, heart,

and brain

• Gametes – sex cells involved in reproduction and

not important as structural components of the

body

• Egg cells produced in female ovaries

• Sperm cells produced n male testes

• Zygote – union of sex cells to form the potential of

developing into a new individual; in this way gametes

transmit genetic information from parent to offspring.

CELL NUCLEUS

• A discrete unit surrounded by a thin membrane, called

the nuclear membrane.

• Inside are two kinds of nucleic acids,

DNA(deoxyribonucleic acid) and RNA (ribonucleic acid)

• Molecules that contain genetic

information that controls the cell’s

function.

CYTOPLASM

• Surrounds the nucleus

• Contains organelles involved in various activities, such

as breaking down nutrients and converting them to

other substances, storing and releasing energy,

releasing waste,

• This is where the manufacturing proteins of proteins or

protein synthesis occurs.

ORGANELLES

• Mitochondria - oval structures enclosed within a folded

membrane, containing their own distinct DNA, called

mitochondrial DNA (mtDNA), produce energy

• Ribosomes – roughly symmetrical and partly composed of

RNA; essential in protein synthesis

DNA STRUCTURE • Cellular function and an organism’s inheritance

depends on the structure and function of DNA.

• DNA is composed of two chains of nucleotides,

comprising a double strand or double helix.

• A nucleotide consists of a sugar, a phosphate, and

one of four nitrogenous bases.

DNA STRUCTURE • Nucleotides 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)

• These two bases are said to be complementary because one

requires the other to form a complete DNA base and can only

bond A/T and G/C.

PART OF A DNA MOLECULE

ENZYMES

• Specialized proteins that initiate and direct

chemical reactions in the body.

• Replication begins when enzymes break the bonds

between bases throughout the DNA molecule,

separating two previously joined strands of

nucleotides and leaving their bases exposed.

DNA REPLICATION

THE DNA REPLICATION PROCESS

1. Enzymes break the bonds between the DNA

molecule.

2. Two nucleotide chains serve as templates for the

formation of a new strand of nucleotides.

3. Unattached nucleotides pair with the appropriate

complementary nucleotide.

PROTEIN SYNTHESIS: AMINO ACIDS

• Small molecules that are the components of

proteins.

• Amino acids are the building blocks of protein.

• Proteins differ according to number of amino acids

and the sequence in which they are arranged

PROTEINS

• Complex, three dimensional molecules that

function through their ability to bind to other

molecules

• The protein hemoglobin, found in red blood cells, is

able to bind to oxygen, which carries it throughout

the body

HORMONES

• Substances (usually proteins) that are produced by

specialized cells and travel to other parts of the

body, where they influence chemical reactions and

regulate various cellular functions.

PROTEIN SYNTHESIS

• Ribosomes help convert the genetic message from

the DNA into proteins.

• Messenger RNA (mRNA) carries the genetic

message from the cell nucleus to the ribosome.

• Transfer RNA (tRNA),found in the cytoplasm, binds to

one specific amino acid.

RNA AND DNA

RNA differs from DNA in three important ways:

1. It’s usually single-stranded. (This is true of

the forms we discuss, but it’s not true for

all.)

2. It contains a different type of sugar.

3. It contains the base uracil as a substitute

for the DNA base thymine. (Uracil is

attracted to adenine, just as thymine is.)

MESSENGER RNA (MRNA)

• A form of RNA that’s assembled on a sequence of

DNA bases.

• It carries the DNA code to the ribosome during

protein synthesis.

TRANSFER RNA (TRNA)

• The type of RNA that binds to amino acids and

transports them to the ribosome during protein

synthesis.

PROTEIN SYNTHESIS: TRANSCRIPTION

• The process of coding a genetic message for a

particular protein.

• A portion of the DNA unwinds and serves as a

template for the formation of a mRNA strand.

TRANSCRIPTION

• The two DNA strands have partly separated.

• Free messenger RNA (mRNA) nucleotides

have been drawn to the template strand,

and a strand of mRNA is being made.

• Note that the mRNA strand will exactly

complement the DNA template strand,

except that uracil (U) replaces thymine (T).

TRANSCRIPTION

PROTEIN SYNTHESIS: TRANSLATION

• The mRNA travels through the nuclear membrane to the ribosome.

• tRNAs arrive at the ribosome carrying their specific amino acids.

• The base triplets on the tRNA match up with the codons on the mRNA.

• As each tRNA line up in the sequence of mRNA codons their amino acids link to form a protein.

WHAT IS A GENE?

• A gene is the entire sequence of DNA bases responsible for the synthesis of a protein.

• A mutation occurs when the sequence of bases in a gene is altered.

• Mutations may interfere with the ability to produce vital protein and may lead to a new variety within the species, hence, evolution.

GENETICS

• The study of gene structure and action, and the

patterns of inheritance of traits from parent to

offspring.

• Genetic mechanisms are the foundation for

evolutionary change.

REGULATORY GENES

• Genes that code for the production of proteins that

can bind to DNA and modify the action of genes.

• Many are active only during certain stages of

development.

HOMEOBOX GENES (HOX GENES)

• An evolutionarily ancient family of regulatory genes

(highly conserved) that determines the

development of the overall organism i.e.. body

shape size and the unique body tissue such as

organs.

VERTEBRAE AND HOX GENES

• The cervical vertebrae (a) have characteristics that differentiate them from the thoracic vertebrae (b) attached to the ribs, and the lumbar vertebrae (c) of the lower back.

• Hox genes determine the overall pattern of each type of vertebra and of each individual vertebra.

CELL DIVISION

• Cell division results in production of new cells.

• During cell division: • Cells are involved with normal cellular and metabolic

processes.

• The cell’s DNA becomes tightly coiled.

• DNA is visible under a microscope as chromosomes.

CHROMOSOMES

• Scanning electron micrograph of human chromosomes during cell division.

• Note that these chromosomes are composed of two strands, or two DNA molecules.

CHROMOSOME STRUCTURE

• A chromosome is composed of DNA and associated proteins.

• During normal cell functions, chromosomes exist as single-stranded structures.

• During cell division, chromosomes consist of two strands of DNA joined at the centromere.

• Since the DNA molecules have replicated, one strand of a chromosome is an exact copy of the other.

CHROMOSOMES AND GENETICS

• Each species is characterized by a specific number of chromosomes. • Humans have 46 chromosomes.

• 23 from each parent

• Chromosome pairs are called homologus: • They carry genetic information that influences the

same traits.

• They are not genetically identical.

TYPES OF CHROMOSOMES

• Autosomes - govern all physical characteristics except sex determination.

• Sex chromosomes - X and Y chromosome.

• Mammal females have two X chromosomes.

• Mammal males have one X and one Y chromosome.

MITOSIS

• Mitosis is cell division in somatic cells.

• Mitosis occurs during growth and repair/ replacement of tissues.

• The result of mitosis is two identical daughter cells that

are genetically identical to the original cell.

STEPS IN MITOSIS

1. The 46 chromosomes line up in the center of the cell.

2. The chromosomes are pulled apart at the centromere.

3. The strands separate and move to opposite ends of the dividing cell.

4. The cell membrane pinches in and two new cells exist.

MITOSIS

• The cell is involved

in metabolic

activities.

• DNA replication

occurs, but

chromosomes are

not visible.

MITOSIS

• The nuclear

membrane

disappears, and

double-stranded

chromosomes are

visible.

MITOSIS

• The chromosomes

align themselves at

the center of the

cell.

MITOSIS

• The chromosomes

split at the

centromere, and

the strands

separate and move

to opposite ends of

the dividing cell.

MITOSIS

• The cell membrane

pinches in as the

cell continues to

divide.

• The chromosomes

begin to uncoil (not

shown here).

MITOSIS

• After mitosis is

complete, there

are two identical

daughter cells.

• The nuclear

membrane is

present, and

chromosomes are

no longer visible.

MEIOSIS

• Cell division in specialized cells in ovaries and testes.

• Meiosis involves two divisions and results in four

daughter cells, each containing only half the original

number of chromosomes.

• These cells can develop into gametes.

MEIOSIS

RECOMBINATION

• Sometimes called crossing over; the sharing of some

genetic material between partner chromosomes

during meiosis.

EVOLUTIONARY SIGNIFICANCE OF MEIOSIS

• Meiosis and sexual reproduction are highly important evolutionary innovations.

• Meiosis increases genetic variation at a faster rate than mutation.

• Offspring in sexually reproducing species represent the

combination of genetic information from two parents.

PROBLEMS WITH MEIOSIS

• In order for fetal development to occur normally, the

meiotic process needs to be exact

• If chromosomes or chromosome strands do not

separate during either of the two divisions, serious

problems can develop

• Failure to separate is called nondisjunction

POLYMERASE CHAIN REACTION (PCR)

• Allows scientists to make of copies of DNA samples which can then be analyzed.

• Scientists use PCR to:

• Examine nucleotide sequences in Neandertal fossils and Egyptian mummies

• Identify individuals in the case of remains, crime or family relation.

DNA FINGERPRINTS

• Eight DNA fingerprints,

one of which is from a

blood sample left at

an actual crime scene.

• The other seven are

from suspects.

• By comparing the

banding patterns, it is

easy to identify the

guilty person.

RECOMBINANT DNA TECHNOLOGY

• A process in which genes from the cell of one

species are transferred to somatic cells or gametes

of another species.

• Production of human gene products such as insulin

• Genetic manipulation

CLONES

• Organisms that are genetically identical to another

organism.

• The term may also be used in referring to

genetically identical DNA segments, molecules,

and cells.

HUMAN GENOME PROJECT

• Effort begun in 1990 to sequence the entire human

genome, which consists of some 3 billion bases

comprising approximately 25,000 to 30,000 genes.

• The goal was achieved in 2003.

• Scientists are still several years away from identifying

the functions of many of the proteins produced by

these genes.