Chpt 2

Question 1

what was discovered in the early nineteenth century that hardened or “fixed” brain tissue

Answer 1

-tissues immersed in formaldehyde were hardened, and they discovered a special device called the microtome to make very thin slices

Question 2

what is histology?

Answer 2

The microscopic study of the structure of tissues

Question 3

describe Nissl stain and clumps

Answer 3

• basic dyes would stain the nuclei of all cells as well as clumps of material surrounding the nuclei of neurons
• these clumps are called nissl bodies, and the stain is known as the nissl stain

Question 4

how is the Nissl stain useful?

Answer 4

-distinguished between neurons and glia
-enables histologists to study the arrangement or cytoarchitecture of neurons in different parts of the brain

Question 5

what is Golgi stain

Answer 5

-soaking brain tissue in silver chromate solution makes small percentage of neurons darkly coloured in their entirety

Question 6

what does the golgi stain reveal

Answer 6

-neuronal cell body, the region of the neuron around the nucleus that is shown with the Nissl stain, is actually only a small fraction of the total structure of the neuron
-Golgi stain shows neurons have at least 2 distinguishable parts, central region (contains nucleus) and numerous thin tubes that radiate away from the central region

Question 7

What are neurites?

Answer 7

two types: axons and dendrites

Question 8

what was the opposing ideas of Golgi and Cajal?

Answer 8

-Golgi believed cells were fused together to form a continuous reticulum, or network – brain is exception to the cell theory
-Cajal argued neurites of different neurons are not continuous with each other and communicate by contact, not continuity

Question 9

what is neuron doctrine

Answer 9

-the idea that cell theory also applies to neurons

Question 10

what is the diameter of cell body (soma) of typical neuron

Answer 10

about 20 micrometres

Question 11

what is the cytosol?

Answer 11

watery fluid inside the cell, salty, potassium-rich solution that is separated from the outside by neuronal membrane

Question 12

what are organelles?

Answer 12

membrane-enclosed structures (mainly within the soma where there are a number of them)

Question 13

what is the cytoplasm?

Answer 13

everything contained within the confines of the cell membrane, including organelles (nucleus, rough ER, smooth ER, Golgi apparatus, mitochondria), but excluding the nucleus

Question 14

what is the diameter of the nucleus and what is it contained in?

Answer 14

about 5 - 10 micrometres, contained within a double membrane called nuclear envelope (nuclear envelope perforated by pores about 0.1 micrometres across)

Question 15

where are chromosomes located and what do they contain?

Answer 15

-Within the nucleus and contains genetic material DNA (deoxyribonucleic acid)
-each chromosome contains an uninterrupted double-strand braid of DNA, 2 nm wide

Question 16

Where is the blueprint of your entire body contained?

Answer 16

In your DNA

Question 17

The DNA in each of your neurons is the same, and it is the same as the DNA in the cells of your liver and kidney and other organs, true or false?

Answer 17

True

Question 18

What distinguishes different cells from one another (for example neurons and liver cells)

Answer 18

-Specific parts of the DNA that are used to assemble the cell, called genes

Question 19

if the DNA from the 46 chromosomes were laid out straight, end to end, it would measure…

Answer 19

more than 2 m in length

Question 20

what is the “reading” of the DNA known as?

Answer 20

gene expression

Question 21

what is the final product of gene expression?

Answer 21

synthesis of molecules called proteins

Question 22

what is protein synthesis and where does it occur

Answer 22

The assembly of protein molecules, occurs in cytoplasm

Question 23

Why must an intermediary carry the genetic message to the sites of protein synthesis in the cytoplasm? And what performs this funcion

Answer 23

-Because DNA never leaves the nucleus
-performed by another long molecule called messenger ribonucleic acid (mRNA)

Question 24

what does the mRNA consist of?

Answer 24

4 different nucleic acids strung together in various sequences to form a chain

Question 25

what does a sequence of nucleic acids in a chain represent?

Answer 25

The information in the gene

Question 26

What is transcription?

Answer 26

The process of assembling a piece of mRNA that contains the information of a gene --> the resulting mRNA is called the transcript

Question 27

what is the promoter?

Answer 27

The region where the RNA-synthesizing enzyme, RNA polymerase, binds to initiate transcription.

Question 28

What are transcription factors?

Answer 28

the binding of the polymerase to the promoter is tightly regulated by other proteins called transcription factors

Question 29

What is the terminator?

Answer 29

-aka stop sequence -other end of the promoter, the RNA polymerase recognises as the end point for transcription

Question 30

what are introns and exons?

Answer 30

-introns are additional stretched of DNA within the gene that cannot be used to code for protein -exons are the coding sequences

Question 31

What is RNA splicing?

Answer 31

initial transcripts contain both introns and exons, by RNA splicing, the introns are removes and the remaining exons are fused together

Question 32

What does "alternatively spliced" mean?

Answer 32

specific exons are also removed with the introns, leaving an "alternatively spliced" mRNA that actually encodes a different protein --> thus a single gene can ultimately give rise to several different mRNAs and protein products

Question 33

where does mRNA transcripts emerge and where does it travel? And what happens then?

Answer 33

-Emerges from the nucleus via pores in the nucleus envelope and travel to the sites of protein synthesis elsewhere in the neuron -At these sites a protein molecule is assembled much as the mRNA was: by linking together many small molecules into a chain.

Question 34

what are the building blocks of protein?

Answer 34

amino acids, 20 different kinds

Question 35

what is translation?

Answer 35

assembly of proteins from amino acids under the direction of mRNA

Question 36

What is the "central dogma" of molecular biology?

Answer 36

DNA --(transcription)--> mRNA --(Translation)--> Protein

Question 37

what is the human genome?

Answer 37

the entire length of the DNA that comprises the genetic information in our chromosomes

Question 38

What is gene copy number variation?

Answer 38

-DNA contains missing or duplicated genes - occurs at the moment of conception

Question 39

what is a single nucleotide polymorphism mutation?

Answer 39

-"typographical errors" analogous to a minor misspelling caused by a change in a single letter

Question 40

what is genetic engineering?

Answer 40

Ways to change organisms by design with gene mutations or insertions

Question 41

what are knockout mice?

Answer 41

one gene has been deleted (or "knocked out")

Question 42

what are transgenic mice?

Answer 42

genes have been introduced and overexpressed; These new genes are called transgenes

Question 43

What are knock-in mice?

Answer 43

Native gene is replaced with a modified transgene

Question 44

where does protein synthesis occur?

Answer 44

At dense globular structures in the cytoplasm called ribosomes

Question 45

How is protein made at the ribosomes?

Answer 45

mRNA transcripts bind to the ribosomes, and the ribosomes translate the instructions contained in the mRNA to assemble a protein molecule -- ribosomes use the blueprint provided by the mRNA to manufacture proteins from raw material in the form of amino acids

Question 46

describe the rough endoplasmic reticulum (rough ER)

Answer 46

-abounds in neurons -they are nissl bodies, this is the organelle stained with the dyes that nissl introduced -major site of protein synthesis because there are many ribosomes in this region

Question 47

what are free ribosomes and polyribosomes?

Answer 47

-free ribosomes are free floating ribosomes -polyribosomes are several free ribosomes that appear to be attached by a thread --> the thread is a single strand of mRNA and the associated ribosomes are working on it to make multiple copes of the same protein

Question 48

what is the difference between proteins synthesized on the rough ER and those synthesized on the free ribosomes?

Answer 48

-depends on intended fate of protein molecule -if its destined to reside within the cytosol of the neuron, then the protein's mRNA transcript shuns the ribosomes of the rough ER and gravitates toward the free ribosomes -if the protein is destined to be inserted into the membrane of the cell or an organelle, then it is synthesized on the rough ER

Question 49

describe the smooth endoplasmic reticulum (smooth ER)

Answer 49

-stacks of membranous organelles that look like rough ER without the ribosomes -is heterogeneous and performs different functions in different locations -some smooth ER is continuous with rough ER and believed to be a site where proteins that jut out from the membrane are carefully folded, giving them their 3D structure -other types of smooth ER play no direct role in the processing of protein molecules but instead regulate the internal concentration of substances such as calcium