Lecture 1 - DNA, Genes & Chromosomes

What does DNA store?

genetic information

Where is genetic information stored?

in the genes

What is affected when turning on a gene or gene expression?

the organism is

What happens during the process that these controls are in place or get lost?

gene regulation controls occur during this process

How does DNA power the cells?

through encoding for the proteins that provide it structure and do much of the work of the cells

How many copies of each gene do humans typically inherit?

one copy from each parent

Inheritance of alleles of genes from ?

parents to offspring

Where are genes encoded?

in the long DNA molecules that are found within cells organized as chromosomes

A child inheritance gene that make them naturally tall, but they grow up in an environment with poor nutrition. What is the most likely outcome?

the child will be shorter than their genetic potential because their environment matters.

What does DNA stand for?

deoxyribonucleic acid 

What does the structure of DNA inhibit it to do?

to store and transmit genetic information

True or false. Not, only does the genotype matter when inheritancing the alleles of genes from parnets to offspring but alos the environment and the lifestyle condition contribute to the phenotype being produced.

True

True or false. Both copies of the gene are always active

False

What experiment determined that there was an unknown molecule that enabled the inheritance of certain traits/conditions from parent to offspring ?

the griffith’s experiment 

What was Griffith’s experiment about?

It about a test of a different types of bacteria strains being injected on the genetically identical rats in which, one strain of bacteria was virulent (toxic) and the other was nonvirulent (non-toxic). But when the killed virulent bacteria was injected the rat lived. But then when the killed virulent and live nonvirulent bacteria was injected the rat was dead. Hence, making him conculde that their was something in the bacterial strain, a molecule that allowed for the passing of traits/ diease.

How are the parental alleles of the genes turned on/off through the environmental lifstyle conditions?

through being mediated by the chemical modification of DNA = epigenetic

What is imprinting?

Imprinting is when only one of the parental copies are expressed and the other is silenced.

True or false. child inherit a gene that influence metabolism. Only the parental allele

of the gene is active. This is called a parent of origin effect on gene expression ( imprinting ). The child also grows up an environment with a high calorie diet. Hence, the child's metabolism will

be influenced by the parental gene and the high calorie diet.

True.

What was the experiment called in which it was concluded that the unknown hereditary molecule in the Griffith experiment was, in fact DNA?

Avery, Macleod and Mccarty’s experiment

What was Avery, Macleod and Mccarty’s experiment about?

Using the virulent heat killed extracted bacteria was combining it with various different enzymes that would remove that type of marcomolecule selectively and they did it using solution only (control), RNase (removes RNA), ptotease (removes protein), DNase (remving DNA). And when they used the DNase + solution and added it to the nonvirulent bacteria they found out it produced non-virulent bacteria which concludes that you cannot pass on that virulence from the heat-killed virulence bacteria to the live-virulence bacteria if you don’t have DNA as a facter in the solution.

What type of marcomolecule is DNA built from?

nucleotides

What are the 3 components that compose DNA?

a phosphate group, deoxyribose sugar (dehydrated one) and  any one of the nitrogenous bases

What are the two different types of the 5’ memeber sugar ring?

ribose & deoxyribose sugar

What are the names of the 4 different nitrogenous bases?

• Adenine (A)

• Guanine (G)

• Thymine (T)

• Cytosine (C)

What 2 nitrogenous bases would you classify as a purine?

Adenine (A) and Guanine (G)

What is the difference between purine and pyrimidines?

purines (2-membered sugar rings) and pyrimidines (one membered sugar)

What 2 nitrogenous bases would you classify as pyrimidines?

Thymine (T) and Cytosine (C)

What the difference between nucleoside & nucleoside monophosphate?

Nucleoside = sugar + base

Nucleoside monophosphate = sugar + base + phosphate (otherwise, can be called as ‘ nucleotide’)

What is the building block of DNA?

Nucleoside triphosphate

Why is nucleoside triphosphate the building block of DNA?

since it uses the enzyme - ‘ DNA polymerase’ to start building DNA together 

How does DNA attach these nucleotide building blocks together?

through the use of phosphodiester bonds (forming a bond between the 3’ carbon -OH and the attaching to the 5’ phosphate of the next nucleotide)

In which direction, does DNA run?

form the 5’ - AGCT - 3’ direction always

Why aren't nucleosides incorporated into the DNA?

There are no phosphates to make the phosphodiester bonds.

What is the exterior and the interior of the DNA molecule?

• the 2 strands of sugar phosphate winds around the outside of the molecule (exterior of the molecule)

• the nitrogenous bases pointing inward away from the (aq) solution bond in such a way that they hold the 2 strands together  (interior of the molecules) 

Fill in the blanks, two strands of the DNA are __________________, which means that they run in the opposite direction?

antiparallel

Why is DNA held together in such a way that the shape of the configuration of this molecule is always a double helix shape?

due to the base pairing that occurs between the nitrogenous bases

How does the 2 strands of DNA run if, they are antiparallel?

1 strand ; 5’ - 3’ (above on the same side)

2 strand ; 5’ - 3’ (below on the same side )

How do the nitrogenous bases work and connect together?

through the use of some rules such that the….

A = T and C = G always pair together

How are these base pairing interactions actually happening?

through hydrogen bonding that are located on antiparallel strand to each other

Do A=T and G=C bind in the same way?

No, as they produce a specific geometric configuration that is distinct from the geometry of other base pairing interaction due to the different molecules that theses atoms bind to.

In the DNA of certain bacterial cells, 16% of the nucleotides are adenine. What are the

percentage of the other nucleotides in the DNA?

16% thymidine, 34% guanine, 34% cytosine

Fill in the blanks.

% A = % ____

% G = % ____

T , C

What type of bond are the G and C nitrogenous bases held together by?

hydrogen bonds in an antiparallel of the backbone (configuration)

What does the ‘DNA polymerase’ enzyme do?

The enzyme detects the geometry of the base pairs and proofreads it, distinguishing the geometry of both different types of base pairing interactions.

What are the 2 features that contribute to the stability of the DNA?

the hydrogen bonding and the base stacking.

How does base stacking work?

Base stacking works in such a way that the hydrophobic planar ring like structures form in such a way that they like to keep the rings structures one on top of the other producing an additive force making the structure further stable. Alongside with the hydrogen bonding keeping both nitrogenous bases together.

In both humans & eukaryotes, how are DNA compacted?

in our cells

Why is DNA compacted in our cells?

as they are too long to fit within the diameter of the cell 

How many chromosomes does each of our DNA molecules form in an eukaryotic cell?

one chromosome = one linear DNA molecule

What is DNA always packed with?

proteins

What are proteins known as in DNA?

histones

How do histones interact with DNA?

they interact in a way that disregardes the sequence 

What is it called when DNA is complexed with histones?

chromatin

What is a chromatin?

It’s a form of DNA that makes up chromosomes within our cells

What are the steps involved in turning chromatin into chromosomes within our cells?

1. DNA molecules wrap around histone proteins

2. These histone proteins wrapped around in DNA further wrap themselves into a fibre-like structure (compacting down the DNA further)

3. This fibre-like structure forms solenoids (coiled coil of chromatin fiber)

4. Which then all condense down into these chromatids

What 2 types of amino acids are histone proteins rich in that aid with building proteins?

lysine & arginine, which are strong (+) charged amino acids at human body pH

Why do we need positively charged amino acids in our histone proteins for DNA to function?

Since, the sugar phosphate backbone of DNA, has (-) charge at human pH . Hence, DNA generally has a (-) charge in general. When the histone proteins have this (+) charge it enables the wrap of DNA around these proteins to be very stable since, (-) from DNA and (+) histone proteins attach with each other.

What are the total number of pairs of chromosomes we have?

23

What is the breakdown of the 23 pairs of chromosomes?

22 autosomes and 1 pair of sex chromosomes ( X or Y )

Where are each pair of chromosomes from?

one from the biological mother and the other from the biological father 

DNA is packaged with _____________ composed of ________________ forming a chromosome.

histones , chromatin

Along the sequences of those chromosomes, wel all have one _______________________.

1 helical DNA molecule

Along the sequences of those chromosomes, all we have is one helical DNA molecule, and along those sequences are what?

bases and some of these sequences are ‘genes’.

What is this process called when we ‘need to make copies of DNA’ ?

replication

What happens if their is a error present within the DNA replication?

mutations will then occur in the DNA