Meiosis: GCSE Biology Exam

SEX. SEX SEX SEX. Gametes.

There's a strong link between those words. Gametes are sex cells. If you cring at the the word sex, you probably want to be looking at the year 9 science bite size. Sorry.

Meiosis

This is the thing I struggle with the most. Got my book at the ready. Some key things to know before I begin fumbling through this topic:

• Meiosis produces four haploid nuclei. The chromosomes in these are not identical. I repeat, NOT IDENTICAL.
• Meiosis only happens in the reproductive organs like the testes and ovaries. If you don't know what the testes are, it's the 2 bits near your penis. If you don't know what a penis is... 
• Meiosis makes new cells that have half the original number of chromosomes.

I over complicate this all the time so i'll keep it simple.

If you didn't understand the diagram:

Maths terms: Doubles, halves and halves. (x2/2/2)

Ellie Griffin terms (thank god for her): If you make 6 cakes each for friends and have 4 friends you double the mixture to make 12 cakes, and then double them to make 24 and now you have enough! This backwards is simply divided by 4. 4 Haploid gametes.

Sorry this one is a bit crap... had to have Ellie explain it to me. Thank god for friends eh? 

Mitosis: GCSE Biology Exam

Mitosis and Meiosis (covered in another article) are key things to learn. I smell a possible six marker. Unlike someone I used to know... Oh yeah... you wont get that... He couldn't smell. MOVING ON. As with Biology it is a good idea to know definitions so get listening:

"Mitosis makes new cells for growth and repair."

There are lots of details unlikely to come up on the exam but a few things you might wanna know before I start rambling:

• Human body cells are diploid (2 versions of each chromosome, one from each parent)
• 23 pairs of chromosomes in in a human cell.

So:

Mitosis

Mitosis results in two identical cells. The cell gets the signal to duplicate the DNA in order to divide. The cells then have to go from being stringy things into pairs of arms to make chromosomes. In an x shape.

See? X shaped. Wasn't even lying this time.

WARNING: Although often depicted as different coloured arms of the chromosome the 2 arms of the chromosome are EXACT DUPLICATES.

Next comes the line-up. Like in the military and stuff. The chromosomes line up at the center of the cell and the cell fibres pull them apart. Not so much like the military. This is called the "Metaphase" but don't stress about that, not important!

The membranes form around the the new sets of chromosomes. These become the nuclei of the two cells. See where this is going?

Hehehehe... Cleavage.

Finally the cytoplasm divides! The chromomes return to their stringy origins within the new cells. There are now two new diploid cells with exactly the same DNA. This is called being "Genetically identical". Why? Because their genes are identical. Common sense people.

USEFUL FACT: Asexual reproduction uses Mitosis. You might get a question involving plant "runners". These plants use mitosis so when they produce new plants on the ends of these runners they will be genetically the same so are more likely to be the same size and have the same resistance to certain drugs as the original plant. Farmers often use this to breed larger plants by only killing smaller ones... Adds new meaning to the phrase "size matters" doesn't it? 

Protein Synthesis: GCSE Biology

Protein Synthesis is the hardest thing I've ever had to deal with... Well the second hardest. 1



Since it's difficult I thought I would try to format it a bit different. If not for you, so I can at least understand it.

Key Words: 

• Transcription
• Translation
• mRNA (Messenger RNA)
• RNA (Ribonucleic acid, a nucleic acid present in all living cells. Its principal role is to act as a messenger carrying instructions from DNA)
• Codons (A triplet of bases)
• Ribosome (Or big Riby if you wish)
• tRNA 

First thing to remember PROTEINS ARE IMPORTANT. They are key in GROWTH AND BODY CHANGES. I will split this into the 2 stages:

Transcription:

2 DNA strands unzip. These are Complementary. This means the the strand is exactly the same. If it helps you to remember:

"Why, what a nice whip you have there! I also have the same model." 

This is a compliment and they have the same whip. Let's not go into details on that. Each to their own.

The mRNA molecule moves out of the nucleus and joins with a ribosome.

"I shall call him Riby and he shall be mine and he shall be my Riby. Come on, Riby Come on, little Riby."

The reason I put these crap jokes in is in hope that you might remember it in the exam and think oh I remember that guy trying to be funny with that stupid Riby joke... Riby... Ribosome! Boom, 1 more mark.

Anyhow, moving on. This brings us onto the following stage:

Translation

Amino acids are brought to big Riby by tRNA molecules. Why? Because the Ribosome is effectively a glue stick. It sticks the Amino Acids together in a chain to make a protein chain (polypeptide). "These follow the order of the triplet of bases called codons in the mRNA." A big sentence to simply say they are in 3s.

All of this ends up creating a protein that, due to the enzymes bringing the correct Amino acids, can do a certain job.

So if this confused you even more, i'll try and sum it up:

1. DNA Strands Unzip and complementary strand is created, this is mRNA. (TRANSCRIPTION) 
2. mRNA joins with Ribosome.
3. Amino acids specially selected by tRNA and brought to the Ribosome.
4. Ribosome sticks the amino acids together in codons. (TRANSLATION)

Well, I really hope this didn't confuse you more. Drop us a comment if it did and i'll answer best I can. 

1.The hardest thing was amalgamated algorithms, get your head out of the gutter.

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The Human Genome Project: GCSE Biology

My exam board says about the Human Genome project and needing to know the for points and the againsts. This will be a very short blog on it. As with all of my blogs it's mainly for my revision.

The "Human Genome Project" is a project to map all of the human genes. The idea is to collaborate all the scientists they could find to do this.

A simple way to remember the for and against points is to imagine this:

You are the manager of a company. You need to find a new security guard. This job requires, good eyesight, good hearing, strength and intelligence. You need to find the ideal candidate. This kind of job takes a lot of training to get used to the site they are guarding. Learn the door codes, learn the routines, learn the little hiding places for thieves. 

So this is where the human genome project becomes useful. Suddenly, judging from their past relatives, you can see one candidate is likely to get a heart disease later in life. Well, that's him out of the pile! 

Take it from the candidates perspective. No employer is going to employ someone likely to cost them money in sick pay. This is discrimination and is called "Gene-ism". It is a negative point of the Human Genome Project. 

However with this knowledge that you may get a heart disease later on in life means that doctors may be able to reduce the chances of this by informing you of diet changes and lifestyle changes that could save or at least prolong your life. This is "Preventing and Predicting Diseases" and is a positive point of the Human Genome Project.

Knowing what diseases someone may get can be very useful for "Accurate Diagnoses". This is a good point of the Human Genome Project. 

A sort of sci-fi point of the Human Genome Project is that in the future we could determine what a thief looks like from DNA samples. This would "Improve Forensic Science" and is a good point of the Human Genome Project. 

Some insects climb into peoples skin and lay eggs that hatch and then the baby insects slowly eat your skin. Maybe they're on you now... Paranoid? You should be. If you knew you were likely to get a skin disease or a heart condition you would spend your entire life worrying about it every time you looked in the mirror or had a pain in your chest. This is called "Increased Stress" and is a bad point of the Human Genome Project.

I have repeated the name "Human Genome Project" a million times. So DON'T FORGET IT. The red paragraphs are negative and the green positive points about it. What's it? The Human Genome Project. 

Hope it comes up in the exam and it's an easy 4 marks for you. Maybe 6, you could be lucky.

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