Поиск

Полнотекстовый поиск:
Где искать:
везде
только в названии
только в тексте
Выводить:
описание
слова в тексте
только заголовок

Рекомендуем ознакомиться

Остальные работы->Реферат
Going to the movies is fun. You get your candy and your drink and are taken away into a fictional world for two or three hours, then leave the theater...полностью>>
Остальные работы->Реферат
The Opium War only lasted from 1839-1842 and 1856-1860, but it was far more devastating to China’s view as the center of the world. China had always t...полностью>>
Остальные работы->Реферат
From my limited studies of comparative government I have come to the conclusion that a plurality type of electoral process where winner takes all is a...полностью>>
Остальные работы->Реферат
The actions of the human race can be seen, albeit sometimes after careful examination, to be influenced by certain beliefs or values. In some cases th...полностью>>

Главная > Реферат >Остальные работы

Сохрани ссылку в одной из сетей:

Heredity Essay, Research Paper

Deoxyribonucleic acid and ribonucleic acid are two chemical substances

involved

in transmitting genetic information from parent to offspring. It was

known early into the

20th century that chromosomes, the genetic material of cells, contained

DNA. In 1944,

Oswald T. Avery, Colin M. MacLeod, and Maclyn McCarty concluded that DNA

was the

basic genetic component of chromosomes. Later, RNA would be proven to

regulate

protein synthesis. (Miller, 139)

DNA is the genetic material found in most viruses and in all

cellular organisms.

Some viruses do not have DNA, but contain RNA instead. Depending on the

organism,

most DNA is found within a single chromosome like bacteria, or in several

chromosomes

like most other living things. (Heath, 110) DNA can also be found

outside of

chromosomes. It can be found in cell organelles such as plasmids in

bacteria, also in

chloroplasts in plants, and mitochondria in plants and animals.

All DNA molecules contain a set of linked units called

nucleotides. Each

nucleotide is composed of three things. The first is a sugar called

deoxyribose. Attached

to one end of the sugar is a phosphate group, and at the other is one of

several

nitrogenous bases. DNA contains four nitrogenous bases. The first two,

adenine and

guanine, are double-ringed purine compounds. The others, cytosine and

thymine, are

single-ringed pyrimidine compounds. (Miller, 141) Four types of DNA

nucleotides can

be formed, depending on which nitrogenous base is involved.

The phosphate group of each nucleotide bonds with a carbon from

the

deoxyribose. This forms what is called a polynucleotide chain. James D.

Watson and

Francis Crick proved that most DNA consists of two polynucleotide chains

that are

twisted together into a coil, forming a double helix. Watson and Crick

also discovered

that in a double helix, the pairing between bases of the two chains is

highly specific.

Adenine is always linked to thymine by two hydrogen bonds, and guanine is

always linked

to cytosine by three hydrogen bonds. This is known as base pairing.

(Miller, 143)

The DNA of an organism provides two main functions. The first

function is to

provide for protein synthesis, allowing growth and development of the

organism. The

second function is to give all of it s descendants it s own

protein-synthesizing information

by replicating itself and providing each offspring with a copy. The

information within the

bases of DNA is called the genetic code. This specifies the sequence of

amino acids in a

protein. (Grolier Encyclopedia, 1992) DNA does not act directly in the

process of

protein synthesis because it does not leave the nucleus, so a special

ribonucleic acid is used

as a messenger (mRNA). The mRNA carries the genetic information from the

DNA in the

nucleus out to the ribosomes in the cytoplasm during transcription.

(Miller, 76)

This leads to the topic of replication. When DNA replicates, the

two strands of

the double helix separate from one another. While the strands separate,

each nitrogenous

base on each strand attracts it s own complement, which as mentioned

earlier, attaches

with hydrogen bonds. As the bases are bonded an enzyme called DNA

polymerase

combines the phosphate of one nucleotide to the deoxyribose of the

opposite nucleotide.

This forms a new polynucleotide chain. The new DNA strand stays attached

to the old

one through the hydrogen bonds, and together they form a new DNA double

helix

molecule. (Heath, 119) (Miller, 144-145)

As mentioned before, DNA molecules are involved in a process

called protein

synthesis. Without RNA, this process could not be completed. RNA is the

genetic

material of some viruses. RNA molecules are like DNA. They have a long

chain of

macromolecules made up of nucleotides. Each RNA nucleotide is also made

up of three

basic parts. There is a sugar called ribose, and at one end of the sugar

is the phosphate

group, and at the other end is one of several nitrogenous bases. There

are four main

nitrogenous bases found in RNA. There are the double-ringed purine

compounds adenine

and guanine, and there is the single-ringed pyrimidine compounds of uracil

and cytosine.

(Miller, 146)

RNA replication is much like that of DNA s. In RNA synthesis, the

molecule

being copied is one of the two strands of a DNA molecule. So, the

molecule being

created is different from the molecule being copied. This is known as

transcription.

Transcription can be described as a process where information is

transferred from DNA to

RNA. All of this must happen so that messenger RNA can be created, the

actual DNA

cannot leave the nucleus. (Grolier Encyclopedia, 1992)

For transcription to take place, the RNA polymerase enzyme is

needed first

separate the two strands of the double helix, and then create an mRNA

strand, the

messenger. The newly formed mRNA will be a duplicate of one of the

original two

strands. This is assured through base pairing. (Miller, 147)

When information is given from DNA to RNA, it comes coded. The

origin of the

code is directly related to the way the four nitrogenous bases are

arranged in the DNA. It

is important that DNA and RNA control protein synthesis. Proteins control

both the cell s

movement and it s structure. Proteins also direct production of lipids,

carbohydrates, and

nucleotides. DNA and RNA do not actually produce these proteins, but tell

the cell what

to make. (Heath, 111-113)

For a cell to build a protein according to the DNA s request, a

mRNA must first

reach a ribosome. After this has occurred, translation can begin to take

place. Chains of

amino acids are constructed according to the information which has been

carried by the

mRNA. The ribosomes are able to translate the mRNA s information into a

specific

protein. (Heath, 116) This process is also dependent on another type of

RNA called

transfer RNA (tRNA). Cytoplasm contains all amino acids needed for

protein

construction. The tRNA must bring the correct amino acids to the mRNA so

they can be

aligned in the right order by the ribosomes. (Heath, 116) For protein

synthesis to begin,

the two parts of a ribosome must secure itself to a mRNA molecule.

(Miller, 151)


Загрузить файл

Похожие страницы:

  1. Definitions Essay Research Paper Human Growth and

    Реферат >> Остальные работы
    ... on their similarity to each other. 32. attachment: ... muscles and arteries. 88. cross sectional studies: research design ... with many branches. 102. deoxyribonucleic acid(DNA): molecule composed of four ... the biochemical basis of heredity. 103. dependent variable: ...
  2. Biological Revolution Essay Research Paper The Biological

    Реферат >> Остальные работы
    Biological Revolution Essay, Research Paper The Biological Revolution The year ... of genetics, the study of heredity and DNA (deoxyribonucleic acid). People often say it ... should be approached with much research and responsibility. If this is accomplished ...
  3. Untitled Essay Research Paper Morality and the

    Реферат >> Остальные работы
    Untitled Essay, Research Paper Morality and the Human Genome Project MWF ... the cell that controls heredity” (Lee,4). Subsequently, “reasearch and technology efforts aimed at ... of genetic history involved DNA (deoxyribonucleic acid). DNA, as a part of genes ...
  4. Genetic Engineering 3 Essay Research Paper Science

    Реферат >> Остальные работы
    Genetic Engineering 3 Essay, Research Paper Science is a creature that continues ... 16). Inside every person is Deoxyribonucleic acid or more commonly known as ... message of heredity. “Genes constitute a blueprint of our possibilities and limitations, the ...
  5. Genetic Engineering Essay Research Paper Science has

    Реферат >> Остальные работы
    ... Essay, Research Paper Science has allowed for advances in production, transportation and ... deoxyribonucleic acids, or DNA. DNA determines the shape, form and ... entire organism, and its future offspring.” (AGST, 1998: ... of organisms whose heredity has been altered; ...

Хочу больше похожих работ...

Generated in 0.0018610954284668